Refactor makefile

- separate targets for background, content, and test (cut down on
  compile time by only rebuilding what's changed)
Refactoring Fcommand help handling

- intending to use Polymer
- need vulcanize since chrome extension CSP blocks all the inline scripts
  used by Polymer
Example Fcommand doesn't need to be web-accessible
Support --help option for all Fcommands with help

- use with Polymer for look-and-feel niceties (I'm not happy with the
  presentation yet (and I'm not sure paper-dialog is what I want to or
  should use), but it's a WIP)