Merge pull request #173 from Blue-Shadow/master

ZDoom language configurations update
Fix crash on moving a vertex in a map with no lines
Add typed characters to browser filter rather than searching when canvas is focused
Add check for WMP installation in Windows

Disables soundfont-less MIDI and MP3 playback if not installed
Clear scripts on creating new map
Fix possible crash after saving map while in 3d mode
Don't use refresh timer for OGLCanvas when not using SFML RenderWindow

Seems to cause stuttering in the map editor if another OGLCanvas is showing (eg. the map preview in the main editor  window)
Add new archive to recent files on map 'Save As' (or saving a new map)

Also hopefully fixed up focus issues when executing an external program, ie. when building nodes
Add (optional) confirmation dialog on exit
Fix #179 (Crash on exit)
Use inverse scale for UDMF floor/wall scale properties

Fixes #177
Center the texture editor patch browser by default
Correct invalid lines created via line drawing anti-clockwise

Fixes #181
Uncheck textures from base resource by default in 'Remove Unused Textures' function

Close #174
Flip line if second side sector is set with no first side on create sector (#181)
Add SLADE 2 colour configuration
Rename default.txt to Default.txt
Bump version to 3.1.0.1
ZDoom language configurations update
- DECORATE: Added WEAPONSPAWN actor flag.