Fix Panel ListView hover/focus rect image rect.

Convert UI.png back to PNG8 format (8-bit colormap, non-interlaced).
Correct sample material path.
adds mousewheel translation in editor
Added SDL on-screen keyboard support.
Documented the screen keyboard.
Merge remote-tracking branch 'remotes/friesencr/mousewheel-zoom'
For Travis CI - Replace GH_TOKEN as it was exposed in the build log.

Due to git push failure from detached HEAD, the error log in Travis CI build contains GH_TOKEN for worker account. A new GH_TOKEN is now generated.
Enhance the script so that it does not spit out any output or error when pushing. The script still can rely on command exit status, however.
For Travis CI - proceed with API update even when site is up-to-date.

The API documentation update is expected to fail when remote HEAD moves (i.e. there are new pushes while Travis CI build is in progress). Enhance the script one more time so that it always attempts to update API documentation on every build.
Travis CI: API documentation update at 2014-01-05 05:32:55 UTC.
[ci skip]
stores 5 most recently used scenes
Merge remote-tracking branch 'remotes/friesencr/scene-mru'
Misc. tweaks on Editors and minor refactoring.
Exposed ResourceCache::GetFile() to Lua. The file must be manually deleted once no longer needed.
Travis CI: API documentation update at 2014-01-05 18:04:26 UTC.
[ci skip]
Sanitate resource dir similarly when adding and removing it to ensure removing works properly.
Travis CI: API documentation update at 2014-01-05 23:24:56 UTC.
[ci skip]
When removing a resource dir, remove the FileWatcher with matching path instead of relying on the indexing.
Added necessary include files to not rely on includes in Precompiled.h.