Process for adding a new core committer

When a new core committer is named, the following should be done to give them the access and privileges they need.

• In Gitolite, add the new committer's key(s) to the @egcommitters, @osrfcommitters, and @egsecurity groups.
• In Launchpad, add the new committer to the Evergreen Release and the Evergreen Security teams.
• Add them to the security team mailing list.
• Update the list of committers.