Fixes for new properties in MPAppDelegate_Store

[FIXED]     Properties in categories aren't synthesized.  Using fancy new PearlAssociateObjectProperty from Pearl now to make a fake property.
[FIXED]     Show overlay on UI thread.
[FIXED]     ONLY_ACTIVE_ARCH = NO because weird codesign errors happen on second build with it set to YES.
	modified:   External/Pearl
Merge branch 'master' of github.com:Lyndir/MasterPassword