Changed, internal, UDMF: local texture offsets and scale are now copied when merging sidedefs.

Changed, internal: made TextLabel and IRenderer2D public properties compatible with DB2 implementation.
Fixed some more cases when sidedefs belonging to linedefs, which were moved on top of existing linedefs, were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.
Fixed, Map Analysis mode: error checks must be updated after switching map format.