Feature: Icons added for Debug and Release for OS X - option to modify icons for specific projects


Thanks to @NickHardeman for getting this working - I just had to modify it a bit to work with the project generator. 

- Seperate icons for Debug and Release
- For a project that needs a specific icon you can place the files in the data folder and change one line in Project.xconfig to have it use the different icons. 
- Default icons are stores in the openFrameworksCompiled/project/osx/ folder with the other xcode specific files. 

This relates to:  but does not close - #1039