Changed, Visual mode: "Paste Selection" action (Ctrl-V) can now paste both...

Changed, Visual mode: "Paste Selection" action (Ctrl-V) can now paste both copied textures and things, based on what was copied last.
Changed, Map Analysis mode: the view is now much more zoomed after clocking on a "Check very short linedefs" error check result.
Removed single testing engine launchable by the editor at once limitation (it worked properly only when using Test map actions anyway).
Fixed: re-did the fix for invalid geometry created when drawing very large grids from R2653, because it caused other issues.