Added high-lighting for placeholders in tokens in the translation interface
Fixed token hilighting regex, missing $ anchor for placeholder ordering.
Moving screenshot handling out of the Forum controller.

Should hopefully be reusable by other components.
A unique form identifier will be useful.

It's currently only used for threads, but can be used to namespace
screenshots and action_tokens across any and all forms.
Fixing screenshot / token result, was copied from screenshot / thread
Adding 'retired' column to token.
Added a 'fuzzy' field to TokenLanguage

Can be used to mark a translation in need of review if an automated
merge of translations was carried out.
Breaking dropzone component out into its own include template.

%s/thread_form_id/form_id/g since screenshots won't apply to just threads.
Do not count tokens with only invalid translations as done - fixes issue #155
Merge pull request #173 from jbarrett/translation-system-improvements

Initial translation system improvements