Visual Mode: added toggleable option to select all adjacent visual vertex slope handle when selecting a visual slope vertex handle. The action is called "Toggle Adjacent Visual Vertex Slope Selection"

UDBScript: the progress bar in the running script dialog now stops its animation when no progress was set and the script finished.

UDBScript: fixed a problem where the UDB.log() method crashed when a non-string object was passed to it

UDBScript: groups all classes, objects, and methods in a new UDB namespace, usable with the new feature version 4. Updated the documentation accordingly. Resolves #679

Added classic rendering mode to closer emulate software renderer visuals in visual mode

Added "Orbit" and "Move Camera to Cursor" visual mode actions (not bound by default)

Script run by UDBScript are now executed asynchronously

UDBScript: fixed a bug where Map.nearestLinedef, Map.nearestThing, Map.nearestVertex, and Map.nearestSidedef would not return valid objects when no nearest map element was found

Fixed a crash with Mono that happened because of the placeholder text in the "additional parameters" text box in the testing drop down menu. Fixes #677

Event lines are now shown between things and map elements even if the thing doesn't have an action, but directly uses its args. Resolves #676