This changes all variables and functions from using Suspend{ed} to using
Silence{d} as well as documentation, errors and logging.

This puts the verbiage more in line with what the feature does, and
leaves room for other moderation controls in the future.

NOTE: this includes no backend refactoring, which may be confusing. We
should rename things to fit ASAP.

Ref T661

- update error messages to be correct
- move suspended message into template and include for other pages
- check suspended status on all relevant pages and show message if
logged in user is suspended.
- fix possible nil pointer error
- remove changes to db schema files
- add version comment to migration
- add UserStatus type with UserActive and UserSuspended
- change database table to use status column instead of suspended
- update toggle suspended handler to be toggle status in prep for
possible future inclusion of further user statuses