invite: show Contact Details and open petname for editing

The frontend chooses a request-id, sends it to the backend with the
invite request, which then sends it back in a "reqid" tag that
accompanies the announcement of the new addressbook entry. The frontend
is waiting for that reqid, and responds to it by opening the Contact
Details panel and then opening the Petname field for editing (as if the
user had clicked the new addressbook-entry row and then clicked the
"edit" button next to the petname).
invite: remove "petname" field, but auto-edit petname right away
control.html: remove unused+missing "main.js"