Modifications to compile emstudio in OSX environment

Changed the QT projectfile core/core.pro to include OSX correctly. The normal unix section won't work, so I excluded 'macx' from it and made new section for it. This presumes that the qwt and qjson libraries are installed as frameworks into /Library/Frameworks.

Also, the OpenGL headers are different in OSX so I there is a modification for it in tablemap3d.cpp.

I also filled the OSX section in mainwindow.cpp to get the default resource path from the application bundle (Resources). Also to look for a plugin file which is libfreeemsplugin.dylib in OSX.