Add support  for non-root URIs and an easy dev-server launch script

I'm running dmon on a machine with multiple apps with various "context roots" (e.g. /app1, /app2, etc). Out of the box, dmon didn't look for the CSS and JS files in the right place. I added a config variable to set this manually.

Ideally, the root should be identified automagically by the framework / app (a la Django), but Bottle doesn't seem to provide a good mechanism to do this out-of-the-box. Could be a future enhancement.

In any case, this solution seems to work well, is easy to configure, and requires zero configuration if installed at the domain root (no different than today).


Additionally, I wrote a quick and dirty wrapper to launch Bottle's built-in development server if you're writing new features on a non-server system and don't want to configure Apache, nginx, etc. Just run `python util/dev_runner.py` to crank it up.

The dev wrapper defaults to listening only on `localhost:8001.`