Improve overall Mac OS X port of Banshee

by Timo Dörr for GNOME

Banshee's Mac OS X port needs improvement. There are lots of extensions in the Banshee Communnity Extension repo (BCE) that currently can't be build and/or used on OS X. Furthermore, hardware support for syncing devices is mostly not present on the OS X plattform. Goal of this project is to work on these items, as well as introduce some OS X specific features like integrating Mac's media functions, native file dialogs and others.