Disable MINT network monitoring.

We aren't interested in it, and it looks like it converts
ConnectExceptions to its own DelegationExceptions, which breaks the
assumptions in our catch clauses and makes the app crash.
Use correct edit activity for commit comments.
Fix going to user's organization(s).
Refresh pull request event list when changing PR comments.
Mark submodules as such in the file list.

As Github lists them as 'file' in the contents API for backwards
compatibility reasons, we have to track the submodule list via separate
API.
Improve header string for PR comments in event list.
Hide event list header if there's no event.
Make branch/tag switching more clever.

Don't needlessly reload the repo object, and don't reapply initial page
selection on each repo reload.