TODO

* Consider time to render in by_work dequeue strategy?

* Tile proxy enhancements
   - Persistent process to avoid start-up times.  (FastCGI?  WSGI?)
   - Record request statistics: up-to-date, fresh, and old tiles served
   - Record last-served date for tiles so as to expire unaccessed tiles.

* commands to force expiration of tiles in queuemaster

* Rendering enhancements
   
   - Dashed line for intermittent waterways

   - Water-carrying pipelines should be blue

   - Use empty dashed outlines for roads under construction

   - Arrows or other indicators for one-way streets

* Stylesheet enhancements

   - Reorganize locations (put in subdirectory)

   - Clear out unused/unneded ancillary files (symbols, custom-symbols, etc.)