Commits corrections framework

There should be a mechanism for manual corrections of commits data. Each decision on particular correction should pass through standard OpenStack review process. This concept will be implemented as follows:
 * There would be a file with corrections in json format etc/corrections.json.
 * Commit processor will read this file from github via https and apply corrections to data in runtime storage.
 * Corrected record will be propagated to in-memory storage by means of update mechanism
 * Corrected record will be marked on UI by note in commit message

Format of etc/corrections.json:
{
    "corrections": [
        {
            "commit_id": "b5a416ac344160512f95751ae16e6612aefd4a57",
            "correction_comment": "this commit is edited",
            "lines_added": 0,
            "lines_deleted": 0,
            "files_changed": 0
        }
    ]
}