Merge current state of UDB

See merge request STJr/UltimateZoneBuilder!2

- A new "Show Textures" option up on the top bar, which draws any sector not flagged to be hidden on the textured automap
- Holding Shift will highlight sectors instead of lines
- Left-clicking on a highlighted sector will toggle the "Not shown on textured automap" flag
- Textures will be shown when Shift is held down even if the "Show Textures" toggle is off

EDGE Classic Game Configuration: fixed a problem with lighting effects in the generalized sector options. Fixes #875

Edit Selection Mode: fixed a problem where floor and ceiling textures were unintentionally scaled in UDMF when resizing the selection. Fixes #873

Fix mono build on linux

See merge request STJr/UltimateZoneBuilder!1

UDBScript: fixed a problem where floating point default script option values would be converted to the system's locale on hot reloading. Fixes #858

Nodes Viewer Mode: fixed a problem where trying to engage the mode with an empty map could crash. Fixes #857

Map Analysis Mode: fixed a problem where lines with fractional vertex positions could erroneously be reported as overlapping

Thing Edit Form (UDMF): fixed a problem where setting floating point values for health wasn't possible. Fixes #225

Stair Sector Builder Mode: fixed an issue where the number of sectors and the sector depth was not loaded correctly when a default prefab was set. Fixes #847