@ working on NumericTextbox versions with up/down buttons and dropdown lists

- Fixed bug that allowed pasting geometry in visual mode (and the geometry becomes erroneous)

- Highlight and selection colors are now hidden while dragging textures.

- Fixed disappearing temp file in testing parameters when "Use short paths" is checked.
- Added option for resource to exclude them from the testing parameters (for example, you may want to exclude zdoom.pk3)

Fixed a bug where flipping a line resulted in a crash, if its start vertex did not belong to any other line

- Re-enabled UDMF comments for element indices (should work with ZDBSP now)
@ Added test case for triangulation

Fixed a bug that crashes the SurfaceManager sometimes

- Increased spacing for image previews in the information panels so that long texture names can be fully displayed

- Better handling of missing UDMF TEXTMAP fields (Error now includes the element and index at which the field is missing and will not abort loading. Instead it will use a default value.)
- UDMF TEXTMAP now contains the indices of elements as comment next to the structure header.
- Thing cages in Visual Mode now also get the selection and highlight color so that a selection and highlight on things without sprite can also be seen.