Detect diff & merge softwares installed on the developer's workstation and execute them for the approval merge #3

When computing the approval tests and facing an empty or different approved file, the framework should allow merge tools to be executed automatically to review and validate the outputs of the program.

This feature should work on any OS, and here's the first list of supported tools to look for:

Windows support

• IntelliJ IDEA diff tools
• GVim
• KDiff 3
• Beyond Compare 3
• Beyond Compare 4
• TortoiseIDiff
• TortoiseMerge
• WinMergeU
• Araxis Merge
• Code Compare

Linux support

• IntelliJ Ultimate IDEA diff tools
• Beyond Compare
• IntelliJ Community IDEA diff tools
• GVim
• KDiff 3

Mac OS X support

• IntelliJ IDEA diff tools
• KDiff 3
• GVim
• DiffMerge
• Beyond Compare
• Kaleidoscope
• p4merge
• tkdiff

See legacy implementation