[GT-20] Added dialog for lessons selection and buttons to control lessons
Merge branch 'gt-22-addlesson-position2note'

Conflicts:
	GuitarTrainer/res/layout/main2.xml
	GuitarTrainer/src/com/ago/guitartrainer/lessons/SimpleLesson.java
	GuitarTrainer/src/com/ago/guitartrainer/ui/LessonSelectionDialog.java
	GuitarTrainer/src/com/ago/guitartrainer/ui/MainFragment.java