Optimize algorithm that retrieves CI results from Gerrit

New algorithm iterates over drivers and branches and polls corresponding
reviews from Gerrit. Reviews are iterated until vote or comment matching
pattern is found.

Also:
 * CI results are merged into drivers during retrieval. Drivers are stored
   in memcached as part of default-data
 * Enforced capitalized case for release ids
 * Removed unused code from dashboard

Closes bug 1319293
Closes bug 1318051

Change-Id: Id8893deb1fcb7d206830678c2aefe6f5e5751c71