./lib/dbagg/__init__.py
    5:  Change item and source collections into app services
    6:  Added hardcoded meta property 'age' to Item

./lib/dbagg/scan.py
    4:  Remove all use of threading in scan.  It was a bad idea anyway.
    5:  No idle checking.  Die off after awhile, start up again on new queueing
    6:  Change downloader, source scanning, item queue each into app services
    7:  Allow arbitrary scheduling of source scans
    8:  Allow immediate scan of a newly added source
    9:  Removed ChunkyItemQueue.  Early optimization bad.  Trust the Twisted reactor.
   10:  Need a clean way of scheduling tasks
   11:  Adjust feed download time according to measured update frequency.

./lib/dbagg/web.py
    4:  Added meta model for ItemModel