Small style improvments to helpers and baseURI

To be consistent with angular style and our own in-house style
- Change baseurl to baseURI, since that is the normal DOM name for the
  concept
- Change helper to helpers (like controllers, services, etc)
- Wrap the dependency injection annotations on the baseURI factory
  function definition, rather than its use, because the annotations
  should always appear with the definition so they can be easily kept
  in sync