Success message for successful unsubscribe - instead error

Fixes #540

Also add canonical tag to question lists and tag pages.

Determine queued status when fetching from database.
Simplify voting tooltips.

Move functionality to FileCacheDriver, strip down manager class

We now use qa-global.js for all the in-page JS (except for qa-admin.js
which regular visitors don’t need).

Clean up some of the JS code

Defaults to ‘anonymous’

Show/hide field and handle security on backend.

Fixes #487