Use JSON views for requests with the `.json` extension.
Added 404 JSON view.
Updated framework.
Added plugin to enable use of nl2br() wherever format_text() is used.
Merge branch '3.0'

Conflicts:
	vendor/traq/views/default/error/404.json.php
Priorities can now be fetched via the API.
Priorities can now be created via the API.
Priorities can now be updated via the API.
Priorities can now be deleted via the API.
Don't append `.json` to the view filename if it's not being rendered.
Merge branch '3.0'