Document Review Statistics

I suggest the creation of a document explaining the Review Statistics shown when accessing the Reviews tab at the project's home: http://localhost:8060/cru/browse/<project_name>

The statistics are shown as follows:

The one that caused the suggestion to be made was the Days to complete statistic. This metric counts the average time for review when it's in open state (in days). It bases on review changes log and counts changes from last month till "today". So final result is total days count in which reviews were open divided by total count of reviews in that period.

To further explain a change log, every time a review state is changed (created, opened and so on) the status is saved in the database with a timestamp.

To calculate the metric we fetch status logs from last month; entities are fetched in by date order descending, grouped by Review.
So basically we're getting a list of status updates and we're processing them sequentially. The time difference between opening and closing a review is added to total days variable. The metric will be calculated as a division of this total days variable by the total count of processed reviews.