Add banning support to Core

Still a work in progress. Subject to change significantly.
TODO:
Test it.
(DONE) ***Verify that users that are banned can't log in***
(DONE, NEEDS REASON ABILITY) Add banning button to the user detail pages (#192)
(DONE) Add banned search to the search page (192)
(DONE FOR USERS) Add banned detail to the user and character detail pages (192)
(DONE) Modify Schema for #204
(Deferred to later PR.) Add ability to unban.
(DONE) Check for enabled when verifying banned status.

Future PRs: Add ability to specify the reason for a ban, enable/disable subbans, maybe add a secret reason, add ban detail to character pages, add ability to unban a user.