Implemented review processing and stats calculation

* Added review control system module that retrieves reviews from Gerrit
* Refactored runtime storage not to depend on storage contents
* Refactored commit processor and new review processor is added
* Review record processor spawns reviews and marks
* Memory storage is made able to store reviews along with commits
* Migrated to hacking-0.6
* Marks are processed in contribution details and shown on engineer details screen

Implements blueprint review-stats

Change-Id: I80b70de372752cd3d1790da1904c0d423d61e81a