Remove Emulator.RetroArch code
Squashed 'Emulators/Emulator.RetroArch/' content from commit ac5ae3d

git-subtree-dir: Emulators/Emulator.RetroArch
git-subtree-split: ac5ae3d95fcde7897b0d3b9fdb40c50b043edf0e
Merge commit '6c1bf86023a94163ece9e82016a25ddd9167f2c2' as 'Emulators/Emulator.RetroArch'