Significantly reduced video memory usage when pasting sectors. Should also significantly increase speed when pasting many sectors. Fixes #400.

Fixed multi select in 3D Floor Mode to work when starting to drag inside a sector

Fixed a crash in Edit Selection Mode when visual sloping was previously used to make the slope of a sector perfectly planar

Moved smart grid transform into Linedefs Mode and Vertices Mode, so it also works when simply highlighting a linedef or vertex. When doing smart grid transform on a linedef it'll also use the vertex closest to the mouse cursor as the origin instead of always the start vertex

3D Floor Mode: using tab in the 3D floor editor window now cycles through the input fields in a sane order

Fixed a crash that would happen when the line slope things (9500/9501) are used but the linedef they are tagged to doesn't have a front sidedef. Fixes #398.

Added option to select behavior (Tools -> Preferences -> Editing) of scaling when auto-aligning textures on floors/ceilings (use base scale of 1 (default), use current scale as base, never scale)

Aligning textures on the X axis now works correctly with negative scale values when world panning is not enabled.

Fixes for raisesectortonearest and lowersectortonearest action when used on slope handles to account for float rounding errors

The sloping between handles action is now a bit more convenient and tries to figure out what the user wants to do even if not exactly two slope handles are selected.

- Smart pivot handles are now shown for the highlighted slope handle

- Added action to slope selected floors/ceilings between selected slope handles (default key: Ctrl-F)
- Added Shift-W as default key to toggle visual slope picking

- If geometry is selected and the geometry the modified slope handle belongs to is not selected it will now also be modified
- Made the slope handles hover closer to the geometry

Improved drawing length of slope handles on sloped lines (still too short, possibly because of aspect ratio correction?)

The slope handle closes to the mouse cursor will now always be picked (no minimum distance required anymore)

Also fixed some cases where slopes were applied incorrectly

Load previews when they are accessed

Fixed a problem where negative Y scales of sidedefs would result in a wrong offset when auto-aligning