Added NoteSheetCanvas class, refactored DrawToneSheet
Added TactUnit picture to Noteline
Added Tact picture, added function to place a picture in correct proportion
Refactored NoteSheetView
Started drawing of Tones: Drawing body, drawing standard-stem
merged master into branch
Merge branch 'master' into MUS-35_CreateClassesForDrawingDifferentNotes
import cleanup
Merged master into this branch
MUS-39: Fixed Problem with calculating distance to middle Line - signed notes have not to be moved
Merge pull request #34 from Catrobat/MUS-35_CreateClassesForDrawingDifferentNotes

Mus 35 create classes for drawing different notes