Introduce a BaseActivity

* onDestroy() and unbindDrawables() now in BaseActivity where possible
* onOptionsItemSelected() for android.R.id.home now in BaseActivity

I changed the unbindDrawables() call to be more generic.
Source: http://stackoverflow.com/a/5069354

"Proof" that it's the same: LogCat ouput once in the originan ACTIvity
and once in the BASE Activity.

08-14 14:05:25.023: I/BASE(11457):
android.widget.RelativeLayout{41f07968 V.E..... ........ 0,0-768,1038
 #7f07003f app:id/ProjectActivityRoot}
08-14 14:05:25.023: I/ACTI(11457):
android.widget.RelativeLayout{41f07968 V.E..... ........ 0,0-768,1038
 #7f07003f app:id/ProjectActivityRoot}

08-14 14:05:31.770: I/BASE(11457):
android.widget.RelativeLayout{41f8b148 V.E..... ........ 0,0-768,1038
 #7f07002e app:id/MyProjectsActivityRoot}
08-14 14:05:31.770: I/ACTI(11457):
android.widget.RelativeLayout{41f8b148 V.E..... ........ 0,0-768,1038
 #7f07002e app:id/MyProjectsActivityRoot}

08-14 14:05:35.494: I/BASE(11457):
android.widget.LinearLayout{41dc6670 V.E..... ........ 0,0-768,1038
 #7f070027 app:id/main_menu}
08-14 14:05:35.494: I/ACTI(11457):
android.widget.LinearLayout{41dc6670 V.E..... ........ 0,0-768,1038
 #7f070027 app:id/main_menu}