Added some logging conveniences

* Set walrus.Logging to true to enable logging (currently only view
  queries log, minimally.)
* JSServer functions can now call log() as in CouchDB. All arguments
  are stringified and concatenated and written with log.Printf().
Merge branch 'steve' of git://github.com/steveyen/walrus into steve

Conflicts:
	views.go
Simple bucket persistence.

See README for details -- basically, if you call GetBucket with a URL
that's a filesystem path, the bucket will be saved/loaded there.