refactor Category

* move callback bodies to separate methods (easier to test)
added the min-search-term-length site setting
updating cs translation
remove N+1 queries
add fast xor, we need really fast xor to keep our password function honest.
Merge pull request #394 from kubabrecka/cs_update8

updating cs translation
Merge pull request #390 from ZogStriP/min-search-term-length-site-setting

added the min-search-term-length site setting
messagebus diagnostics process path on Mac OS
Merge branch 'refactor-category' of git://github.com/goshakkk/discourse

Conflicts:
	app/models/category.rb
Merge pull request #397 from kubabrecka/fix_ps_warning

messagebus diagnostics process path on Mac OS