Refactoring of UI, added Options menu

* Using the Options menu ("...")
* the NotesView image resized to 250dp, so that the buttons under it are visible
* added About entry to Options menu
* "Settings" moved to Options menu and is not accessed with button any more
Fixed:
* can skip to next question without pausing
* initializing default setting values
Refactored the code from LessonScalegridDegree2Position into ALesson.

Placement of the code into ALesson is supposed to make it reusable by ALesson subclasses.