LCD support, misc. other fixes

Would love to see these changes integrated into trunk. On my branch I have:

- updated the documentation for code as I found it (message types, Ping plugin)
- fixed a couple off-by-one assignments I noticed in du.ino
- **added LCD support** by porting LiquidCrystal to a JS plugin (fixes #15, no protocol changes needed)
- documented LCD support, updated package.js

Big thanks to [&yet](http://andyet.com) for sponsoring this open source work!