Represent insufficient permissions in the UI

[SheaBelsky]

Issue

If I log into CoursePlan and have insufficient permissions to do something, I should see that in the browser.

Replication

1. Go to the web page
2. Log in with Google
3. When you're brought back to the site, nothing happens, but a console warning is logged:

FirebaseError: Missing or insufficient permissions.
    at new e (https://courseplan.io/js/chunk-vendors.f54b8f75.js:1664:524)
    at t.fromRpcStatus (https://courseplan.io/js/chunk-vendors.f54b8f75.js:2116:457)
    at t.fromWatchChange (https://courseplan.io/js/chunk-vendors.f54b8f75.js:2116:8934)
    at e.onMessage (https://courseplan.io/js/chunk-vendors.f54b8f75.js:2019:5977)
    at https://courseplan.io/js/chunk-vendors.f54b8f75.js:2019:4742
    at https://courseplan.io/js/chunk-vendors.f54b8f75.js:2019:5553
    at https://courseplan.io/js/chunk-vendors.f54b8f75.js:1745:9894