Initial crude implementation of an OPIC algorithm that incorporates a
content classifier and exponential backoff/stepup for page change
frequency.  Totally untested; surely broken; ready for discussion :-)
Added SQLite based implementation for OPIC-HITS. Modularized everything.
Merge branch 'master' into opic-discovery
Added emacs backup files to .gitignore
Merge branch 'frontier-objects-as-dict' into opic-discovery
Changes to opic to use new Response/Request models
Lots of improvements to OPIC sqlite
Removed forgotten print statement
Lots of optimizations
Improved virtual page update
Avoid large updates to hits db

This increases performance signifigantly. It needs some more work to avoid errors when used with a persistent database.
Performance improvements
Bugs
Frequency database and tests
Initial link weights database implementation
Stop/Resume crawl. Logging performance
stop/resume test, and some related fixes
Merge branch 'opic-discovery' into development