Remove page size set now we're restoring defaults

* We fixed badly-behaved tests mutating page size state
  and making downstream tests fail. That means this test
  doesn't need to concern itself with setting it.
Add tag button to mappings table

* Display only, currently non functional
No-JS bulk tagging of existing mappings

* We subvert the purpose of params[:http_status], allowing 'tag'
* We use a BulkTagger class with the same interface as BulkEditor
Monkey-patches (to our own classes, no less)

* To avoid deprecation warnings or other nonsense caused by gem clashes