Return int from DB.update
Fix timer related crashes
Remove date picker dialog before showing next one
Fix selection assignment in TaskEditForm
Display proper due time in TaskEditActivity
Fix RestorePostponedRepeatingTasks timer initialization

It was scheduled two times, onResume & onCreate
Add App object for storing constants
Add login dialog, ask user for login data before sync
Extract synchronization code from MainActivity
Merge branch 'feature/user-login' into dev

* feature/user-login:
  Extract synchronization code from MainActivity
  Add login dialog, ask user for login data before sync
  Add App object for storing constants
Show progress dialog while synchronizing, wrap it in AsyncTask
Remove PostponePeriod model
Fix AsyncTask, it's broken because of scalac weirdness

See also https://www.assembla.com/code/scala-eclipse-toolchain/git/nodes/docs/android-examples/android-sdk/Wiktionary/src/com/example/android/wiktionary/MyAsyncTask.java?rev=ad17dd4047ac25b167496db84f4272795eb93c3e
Show progress dialogs while checking credentials & syncing
Merge branch 'feature/progress-spinner' into dev

* feature/progress-spinner:
  Show progress dialogs while checking credentials & syncing
  Fix AsyncTask, it's broken because of scalac weirdness
  Remove PostponePeriod model
  Show progress dialog while synchronizing, wrap it in AsyncTask
Extract TaskList to separate file