removed redundant methods
simplified extrusion overrun logic
removed variable speed from ExtrusionPath
moved lift-logic to GCodePrinter and removed it from moveTo()
refactorings in csg2d construction

* removed indirection through index list, use points directly
* removed flags[] array, introduced set of hull points instead
* renamed polSection to findIndentation and extracted 3 methods
extracted edge collection and conversion into polygon 

into its own class
cleaned up left over method setFirstAndlast()
removed material from LineSegment