[#79445154] Build dashboard urls without any query parameters attached

- `app/extensions/controllers/dashboard.js` checks for the presence of a url and any additional parameters, then strips them, as with the client modifications in https://github.com/alphagov/spotlight/pull/816/files #816
- I've added a test that should show that slugs attached to models should be free of param strings
Get ugly on urls to cut out hashbangs as well as queries

- `url.split("?")[0].split("#")[0];` is fugly but it works
Merge pull request #828 from alphagov/allow_cachebust

[#79445154] Strip cachebust params from module urls