Modifiers: Add "case-sensitive"
User conditions: remove is_shadowbanned

Removes the ability for conditions to be defined based on whether the
author is shadowbanned or not. This is no longer necessary now that
the option to exclude posts from site-wide banned users from the
modqueue exists.

Shadowbanned users' posts can still be set to auto-approve by defining
a condition that matches their username(s) specifically.
Set flair: set on item to prevent overwriting
Placeholders: Add media_ placeholders

Adds support for {{media_user}}, {{media_title}}, and
{{media_description}} placeholders.
Condition: add support for defining priority

Conditions now default to a priority value of 0, and are sorted in
descending order by priority when deciding which order to check them
in. Remove/spam conditions are still checked before all other types.