Gerrit/Code review/Code review hours

(see T128371)

Plan

 * Setup regulary hours for code-review
 * Find an easy way to get changes review faster

Goals

 * Make Code review not stagnating
 * Give people an easy way to find people who would review their changes
 * For people who recived a -1, give them the possibilty to get a third opinion

Process
Note: This is just a draft, and not fully implemented yet
 * Set up code review hour events multiple times a week
 * Ask reviewer to join this hour, and review patches where a review gets requested
 * As developer, search an event which fits for you, and join the channel . To request a review, we can choose one of the following methods:
 * Ask directly on the channel.
 * Provide a table like on Deployment, where any developer can add max one patch per session, a format more suitable if there are several patches to review simultaneously so we can get some order and know what is still to be reviewed.
 * Sign up your patches for review at Phabricator (more bureaucracy).