* [build] option for Java.Interop to be built as non-PCL

Fixes: http://work.devdiv.io/667174

When building a "Hello World" Xamarin.Android app, I noticed the
following in the build log:

    Adding assembly reference for Java.Interop, Version=0.1.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, recursively...
        Adding assembly reference for System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.ComponentModel.Composition, Version=2.0.5.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, recursively...
        Adding assembly reference for System.Diagnostics.Debug, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Threading, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Collections, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Collections.Concurrent, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Reflection, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Linq.Expressions, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Reflection.Primitives, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Dynamic.Runtime, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.ObjectModel, Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Linq, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Runtime.InteropServices, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Runtime.Extensions, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
        Adding assembly reference for System.Reflection.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, recursively...
    Adding assembly reference for Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, recursively...

It appears that Java.Interop is a PCL, and we end up having to work
with lots of facade assemblies during our build!

My thought is that we should build `Java.Interop.dll` the same as
`Mono.Android.dll`:

    <PropertyGroup>
        <NoStdLib>true</NoStdLib>
    </PropertyGroup>
    <ItemGroup>
        <Reference Include="mscorlib">
            <HintPath>$(XAInstallPrefix)xbuild-frameworks\MonoAndroid\v1.0\mscorlib.dll</HintPath>
            <Private>False</Private>
        </Reference>
        <Reference Include="System">
            <HintPath>$(XAInstallPrefix)xbuild-frameworks\MonoAndroid\v1.0\System.dll</HintPath>
            <Private>False</Private>
        </Reference>
        <Reference Include="System.Core">
            <HintPath>$(XAInstallPrefix)xbuild-frameworks\MonoAndroid\v1.0\System.Core.dll</HintPath>
            <Private>False</Private>
        </Reference>
    </ItemGroup>

I added a new property, `$(JavaInteropProfile)` we can set downstream
in Xamarin.Android. We can set this with a
`Configuration.Override.props` file that is already used in
Xamarin.Android's build process.

After doing this, the log now reads:

   Adding assembly reference for Java.Interop, Version=0.1.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, recursively...
   Adding assembly reference for Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, recursively...

And the savings in build times for "Hello World", this is the
`Rebuild` target:
- `Debug` + PCL - 8.424s
- `Release` + PCL - 13.651s
- `Debug` + *not* PCL - 4.258s
- `Release` + *not PCL - 9.487s

That does bring up a big question, however...

Why are facade assemblies adding so much build time???

This change is good: making `Java.Interop` have fewer dependencies.
But I suspect there is more work to be done downstream in
Xamarin.Android. I have a feeling referencing `netstandard` libraries
cause the same problem to occur.

* [build] $(JavaInteropProfile) now outputs to $(Configuration)Net45 folder

This allows us to have two sets of outputs:
- bin/Debug/Java.Interop.dll - referenced by MSBuild tasks
- bin/DebugNet45/Java.Interop.dll - referenced by Mono.Android.dll and apps

Other changes:
- Fixed warning where file was getting imported twice
- Updated `.gitignore` for `*.binlog` files

* Whoops doc XML file was missing

Context: http://work.devdiv.io/667174
Context: dotnet/android#2105
Context: 893562c

Turns Out™ that resolving PCL assemblies within Xamarin.Android is
not as fast as resolving `MonoAndroid`-profile assemblies; see commit
893562c, wherein we see that non-PCL use is 30-50% faster than PCL
assembly use -- shaving off ~4 seconds -- for unknown reasons.

Run with it: allow `Java.Interop.dll` to be built as a
`MonoAndroid,v1.0`-profile assembly in addition to a PCL.
To do this we need to allow `$(TargetFrameworkVersion)` to be
overridden "elsewhere" -- specifically in `Mono.Android.targets`
within the xamarin-android repo -- otherwise `Java.Interop.dll`
will be built for the *wrong* framework profile.

Context: dotnet/android#2157

We believe that we need commit 80b4f4e -- which removes the
`XAIntegrationDebug` and `XAIntegrationRelease` configurations --
applied to xamarin/Java.Interop:d15-9 so that
xamarin/xamarin-android:d15-9 will actually build.