-added baseHelper class for better inheritance
- LabelHelper classes now inherit from baseHelper
- renamed object-dimensions-helper to DimensionsHelper, extracted sub classes
 * also now has BaseHelper as parent class
- added Cross helper : draws ..crosses !
- added SizeHelper (modified ex-sizeArrowHelper):
 * added linewidth setting
 * added ability to toggle left/arrows
 * now inherits from baseHelper
- renamed DistanceArrowHelper to DistanceHelper
- updated Diameter helper:
 * now uses the other helpers as sub elements
 * inherits from BaseHelper
 * overall cleanup
- added LeaderLineHelper to draw LeaderLines