Allow TeamSubmission submitter field to be null
Log some stuff when a tag is created, and tolerate null submitter

Since the website tags ShellAI automatically, the submitter gets set
to None. Now the tagger won't get mad.
Team must have a TeamClient to view submissions
Make TeamSubmission admin readonly
Create a task to add ShellAI tags
Allow tag submitter field to be blank
Remove old TeamSubmission migrations. They're just clutter.
Point TeamSubmissions to TeamClient instead of Team
Handle attempts to tag empty shell repos
Remove submission inline admin from TeamAdmin
Validate uniqueness of tagnames per team
Fix tag_commit signal to use teamclient instead of team
Update views to use TeamClient instead of Team
Merge branch 'changeKey' into feature/submission