Improve flexibility of dependencies locations on OS X

 - Replaced @executable_path by @rpath for more flexibility
 - Updated freetype and sndfile libs as follow:

    install_name_tool -id "@rpath/../Frameworks/freetype.framework/Versions/A/freetype" freetype
    install_name_tool -id "@rpath/../Frameworks/sndfile.framework/Versions/A/sndfile" sndfile
Updated Xcode templates

Since the @loader_path was replaced with @rpath, to correctly load
binaries from within a bundle app we need to add the Frameworks
subdirectory to the run path list.
Merge branch 'feature/rpath_osx'