* api/v1: don't allow multiple tokens with same name
Fail with 422 Unprocessable Entity if the token name
already exist
ref: https://github.com/gogs/gogs/issues/5587
* Move new token error type to models/errors/token
* Remove "useless" ListAccessTokensByName function
* Add an i18n entry for token_name_exists
If a branch was deleted from server, sometimes it is not reflected
on local copy. Therefore, we need to remove the branch with same
name if it is out of sync and then checkout to correct version.
