System-wide support for Unicode emotions and fixes to the Categorize module

# Emoticons

Details in [this](http://chyrp.net/discuss/topic/new-module-emoji/) Chyrp forum thread.

# Categorize fixes

Added option to specify the clean URL for a category – useful if the category name uses international chars. Also fixed a `parse_urls` regex that was causing broken URLs when the blog's Routes > Clean URLs option is disabled. Finally, I spotted and removed some bad markup in edit_category.twig that was creating nested forms.

Details in [this](http://chyrp.net/discuss/topic/categorize-module/) Chyrp forum thread.