Add method Discourse.caughtAjax()

This method functions the same as Discourse.ajax(), except that the dataType is always set to json, and it sets up a catch handler that shows a popup for you.
It would be nice if someone else changed this so that the popup was a modal instead of Bootbox.
Add Zalgo notes to mention.js
Change lots of Discourse.ajax() calls to Discourse.caughtAjax()
Don't need that extra stuff in the static template now
Normalize InputValidation on failed:false because 'ok' isn't even read >.>
Remove failure behavior in success handler - already changed on server

so that we never get a 200 FAIL
Add catches to all calls into Discourse.Draft
Catching stuff in category editing
Make all badge stuff caughtAjax