dynamic tool resizing: updates and refacts

1. Following many suggestions, brushtool has icon now.
2. All sizeable tools wark in the same way.
3. Adjustment circles, they exclusively appear while resizing
dynamically.
4. Some code refact regarding structure and execution speed.
Not used - (sorry)
deleted
Merge branch 'master' of https://github.com/eVoLuTiVeMEDIA/pencil