2Geom sync - initial commit

const ....

Fix false gtk deprecation warnings from gtkmm headers

Fix end type combo box

Toggle button in geometry toolbar to set limiting bounding box for LPELineSegment

Add action to change the end type of line segments if an item has LPELineSegment applied; this is for demonstration purposes because later it would be nice if we could change widgets interactively.

New LPE to draw infinite lines (cut by a limiting bounding box), rays and segments