Tidy up bulk add success messages

* When all are updated, don’t mention “0 created”
* When both updating and creating, don’t show a broken tagged message
(“All .”)
* When tagging, conditionally append “All “ to the start of the
tagged_with string
* When only “1 mapping updated”, remove the full stop as the message is
effectively a title.
Merge pull request #261 from alphagov/fix-broken-modal-title

Tidy up bulk add success messages