Implement shape drag-and-drop

A user may find it useful in some cases to drag and drop a whole shape, instead
of moving each vertex separately. This patch implements shape drag-and-drop by
pressing and holding the right mouse button. Point inclusion algorithm should
work for non-convex and convex polygons, as suggested in
http://www.cs.tufts.edu/comp/163/notes05/point_inclusion_handout.pdf
Merge branch 'shape-drag' of github.com:vliaskov/libremapping

Conflicts:
	MapperGLCanvas.h
	Shape.h
Merge branch 'master' of github.com:libremapping/libremapping