Load test commands at startup

- now that FcommandManager exists, don't store commands in a global cache
Store time of last update per Fcommand

- update Fcommand test to compare the full object, not just the extracted
  data
Fix typo
Correct name of property in bg run request

- this needs tests
Update TODO

- should probably move some methods that access Fcommand data into Fcommand
Log bg data in bgtest fcommand
Refactor to use fcommandManager

- move runBgCode() to Fcommand (it logically belongs there, since it needs
  access to Fcommand internals and can be invoked in two different ways)
- update help retrieval and background script to use fcommandManager
- data passed to bg code is now consistent across both calling contexts
- refactor runBgCode() unit tests (also move them from FactotumBg to
  Fcommand)
Update TODO

- establish best-practices in load-jquery
Update TODO

- how to schedule periodic update checks for Fcommands
- maybe don't use the omnibox at all and instead use a separate hotkey
  to bring up our own UI
Remove obsolete comment

- no longer applies since Fcommand page context code now executes in
  the page itself, and the bg code only ever exists in the bg page
Move dispatch code into onOmniboxInputEntered
Remove obsolete comment

- the suggestion is already modified to indicate internal options
Remove tab check in onOmniboxInputChanged

- the internal-page check was moved into onOmniboxInputEntered to be
  done right before dispatch to the Fcommand