Make it easier to know role "relevance"

[chouseknecht]

From @chouseknecht on October 3, 2017 19:57

Create a task worker that evaluates the level of activity for each role, and determines if a given role has been abandoned. Things to be evaluated:

• Days since last commit
• Days since last closed issue
• Days since last download
• Days since last import

Perhaps each of the above criteria gets a weight? Not sure, but the end result is a score.

Once an 'activity' score is determined it needs to be surfaced on the UI in two ways.

1. A score, indicated through visual queues, that lets the user immediately know the activity level.
2. A filter that allows users to hide or show roles based on activity score.

Copied from original issue: ansible/galaxy-issues#289