Visual Mode: fixed a problem where offsetting the middle texture of double sided lines would not work under certain circumstances. Fixes #702

* Extended rendering options for drawing vertices
* Fixed vertex scale slider behaviour
* Force plot highlighted vertex in DragSectorsMode
* Moved ShouldRenderVertices property into the properties region
* made config file variable lower case to be in line with other config file variables

Visual Mode: added actions to lower and raise map elements by the current grid size (no defaults bound). Resolves #699

Snap selection to grid: fixed a problem that could cause a crash if geometry got removed by snapping it to the grid

Visual Mode: fixed a problem that resulted in incorrect texture offsets when moving a texture by grid size, and the grid was a multiple of the texture size

OBJ Exporter: fixed a problem where the model path controls were disabled unless creation of MODELDEF was enabled. Fixes #692

GZDoom game configuration: added support for distinct upper/middle/lower sidedef brightness levels. Resolves #694

UDBScript: fixed a bug where changing a thing's or linedef's arguments did not recorded for the undo system

GZDoom game configuration: added enum list for the automapstyle UDMF linedef field

UDBScript: fixed a problem where getting a highlighted map element would not work correctly in some circumstances

Fixed a problem where polyobject numbers where not sorted correctly in the editing dialogs. Fixes #690

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