Added Gelbooru.com

Added Gelbooru.com through it's API. Uses crude hack with XMLHttpRequest.
As well as slightly modified doAjaxRequest.
Change doAjaxRequest logic

Changed logic of doAjaxRequest to keep old code and do it non-failure (and decrease headache of @SannySanoff :) )
Ah, and removed commented Sankaku&Danbooru fail
Merge remote-tracking branch 'als/master'

Conflicts:
	web/content_post.js
merged als gelbooru patch
merged als post really