Re-enable texture scaling

See merge request STJr/UltimateZoneBuilder!11

3D Floor Mode: fixed an issue where new control sectors could not be created if any sector's bounding box completely encompassed the Control Sector Area

In Sound Propagation Mode you can set the start (default: Shift+S) and end (default: Shift+E) sectors between which a path the sound can travel will be found and displayed.

Visual Mode: fixed a problem where the selection order was not kept when synchronized selection between visual and classic modes was enabled. Fixes #938

Visual Mode: fixed a problem where things directly touching the top of 3D floors were rendered with the incorrect brightness. Fixes #940

Visual Mode: changes to Eternity Engine's upper/lower texture skewing definitions are now shown in Visual Mode

Fix Wind/Current flags argument

See merge request STJr/UltimateZoneBuilder!12

Visual Mode: fixed a crash when toggling visual vertex slope picking and the map contains double-sided linedefs without a front sidedef. Fixes #928

- fixed an issue where undo snapshots were not created correctly when editing a sidedef's custom UDMF fields. Fixes #920
- fixed an issue where closing the back sidedef's custom UDMF field editing dialog would close the linedef dialog

- fixed a rare condition where skewed mid textures were not clipped correctly
- fixed a problem where translucent mid textures were not skewed correctly
- fixed a problem where sprites were skewed unintentionally