Allow <includePluginDependencies> to be specified for the exec:exec goal - #186

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>3.0.1-SNAPSHOT</version>
    <executions>
        <execution>
            <id>generate-jaxb-classes</id>
            <phase>generate-sources</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <includePluginDependencies>true</includePluginDependencies>
                <executable>java</executable>
                <arguments>
                    <argument>-classpath</argument>
                    <classpath/>
                    <argument>com.sun.tools.xjc.XJCFacade</argument>
                    <argument>-verbose</argument>
                    <argument>-d</argument>
                    <argument>${project.build.directory}/generated-sources/jaxb</argument>
                    <argument>-b</argument>
                    <argument>${project.basedir}/src/main/xjb</argument>
                    <argument>${project.basedir}/src/main/xsd</argument>
                </arguments>
            </configuration>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-xjc</artifactId>
            <version>3.0.0</version>
        </dependency>
    </dependencies>
</plugin>