WebUI: Link for "All PGP Keys" and "TG PGP Keys"

[massar]

We need to rename the current "PGP Keys" link to "All PGP Keys", as that fetches the PGP keys for all Trust Groups somebody is in.

Then add a new link "TG PGP Keys" which just fetches the PGP Keys for that Trust Group.

That would allow people to participate using PGP but while keeping their local keyring small, or per-subject thus avoiding cross-contamination between those groups.

There needs to be a TG-Admin checkbox for hiding the"All PGP Keys" button.