Using user_id instead name for commenters
Construct graph with only one node in case of no pair file (because the two comments has same author). This cause NullPointerException if not create it.
Added property that indicate the commenter is developer (committer).
Added number of commenter that is developer (committer).
Renamed metrics (pull request to issue)
Refatoring: extract cacher methods.
Adding number of improvement and defect task
Fixed query for count number of improvement and defect task by issue list.
Fix query
Fix query