Added handler for clicks on repo groups.

Managing click events on the repo groups via a handler.
Handler reponds to click, introspects group name

The handler is not responding to click events in the groups of repos, and
inspects the source element to find out the name of the group in which the
click event happened.
Now creating fragment to replace repo groups.

When clicking in a group of repos, we now want to replace the fragment
of groups with one containing the list of repos.
Adding the repos to the fragment.

Needs more adjustments.