Active user switching for for password window.

[RENAMED]   MPAppDelegate -> MPMacAppDelegate for Mac to avoid class name confusion in workspace.
[FIXED]     Window behavior when switching user.
More workspace fixes to avoid iOS/Mac confusion by IDE.

[RENAMED]   MPAppDelegate -> MPiOSAppDelegate for iOS to avoid class name confusion in workspace.
Threading fixes for Mac, spinner fix for iOS.

[UPDATED]   TestFlight.
[FIXED]     Mac: References to MPAppDelegate that should be OS-independant now use MPAppDelegate_Shared.
[FIXED]     Mac: Threading and content UI updates.
[FIXED]     iOS: Spinner was showing when going back to unlock VC.