Merge v0.12.1 into master 

## NB Upgrade notes
The normal [upgrade path](https://github.com/eve-seat/seat/blob/master/docs/UPGRADING.md) applies for v.12.0 to v0.12.1.

### Fixes:
- Fix a validation error that prevented accounts from being registered.
- Fix  account statuses not being set to enabled with administratively created accounts.
- Fix a standings typo in the POCO's view (thanks @ccatlett1984)
- Fix administrative account deletion to not soft delete and return API keys owned by the user back to the admin user.

### New:
- Update the login page placeholder to state that usernames or emails are valid logins

#### Release Stats:
*6 commits* in *6 changed files* with *23 additions* and *13 deletions.*