Fixed: render sorting issues with multiple translucent 3D floors next to each other on different heights

Replace the wrong portal_ceil_alpha and portal_floor_alpha with alphaceiling and alphafloor. (#101 by printz)

Fixed: 'Compiling the editor' help page had slightly broken CSS reference. (reported by Kappes Buur)

Fixed: the model should be Z-scaled to 0.83 even in unstretched view to ensure that models fit the geometry right (reported by Ozymandias81)

Fixed: reduced magic in Linedef.SafeDistanceToSq - fixes line/sector selection with 0.125mp grid (reported by camaxide)

Fixed: texture copy/paste in the visual mode was detected as failed pasting and caused a beep. (reported by DOOMGABR, abbuw, Turret_Master)

Fixed: the old way of checking for GZDB's directory writability would not work in certain versions of WINE/Mono

Fixed: cutting a thing in visual mode would leave disposed BaseVisualThings in the selection. (reported by DOOMGABR)

Made Skulltag item sprites optional to support default Skulltag+Zandronum config without producing 100 errors

Updated Zandronum game configurations to include invasion spawners and MBF items (dog, evil sceptre, unholy bible, beta lost soul)