Added IterationEstimate class to calculate the total estimate of all the requirments in an iteration
Added a check in the validate method of the RequirmentsModelValidator
Makes sure the iteration being assaigned is not over yet
Fixed issue where you could not assaign an iteration to a requirement if the last day of the iteratoin was today
Merge remote-tracking branch 'refs/remotes/origin/dev-feature-SchedIteration' into dev