Spelling fix

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>
Comment improvement

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>
Another refactoring of the animation class(es):
 - All animation are now defined in a single ViewAnimator class which a lot less code duplication
 - the "click", "shake" and "alpha" animations can execute runnables at the start and/or end of the animation

Improvements to audio feedback:
 - PlaybackJobs now specify which animation to use (shake or alpha, possibly more later)
 - improvements to animation and exception handling code in AndroidAudioFeedbackController

Improvements to FieldUI:
 - hideField(): fixed bug where audiofeedback would not be stopped due to checking shown state after changing it
 - introduced state field: HIDDEN, SHOWN_ALONE or SHOWN_ON_PAGE

Improvements to FileStorageProvider methods

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>