contacts: prepare actions-populating code for more features

index: document what's happening to contact in authorize/unauthorize handlers

index: authorizing contact also adds it to the roster Maybe there are cases when this doesn't make sense, but so far this looks like the right thing to do.

index: try and use a much newer webrtc-adapter 6.2.1

calls: use rivets more aka the most important shortcut

index: just use <strong> for bold text

calls: show contact's avatar and handle in call area

webrtc: provide contact to Call, fixed hanging up using call area button

.hgignore: add libs/

pipelines: make it easier to see versions of fetched libs