Automatic status updates

1. When we add/update any ResourceBooking we have to check if the corresponding Job has numPositions === length(ResourceBooking with status === "assigned"). And if so, then update the status of the Job to assigned.

2. If we change Job status to cancelled. Then we should change the status of all ~ResourceBooking and~ (updated: don't change status for ResourceBookings) JodCandidate related to this job to cancelled.

Final Submission Guidelines

Git issue link: https://github.com/topcoder-platform/taas-apis/issues/54