Support applying patches from OOUI

Created by: edg2s

This would require a few steps, that should probably only run if an OOUI patch is detected:

1. Check out OOUI to some folder (mediawiki/lib/ooui)
2. Run the build script
3. Copy the files to resources/lib/ooui

While a little complicated and maybe fragile (if the build fails), this would be a big improvement in testing OOUI patches. We can only build from source if required as this may be slower too.