Load the application chrome from view/document instead of the kernel.

- Test for the application explicitly rather than using the kernel's
  heuristic. Prevents attempting to load *component*.vwf.html for
  components referenced by the application.

- Suspend loading the application while the chrome document loads.
  Synthesize a `createdNode` call for the application node when the
  chrome provides a `createdNode` handler. Allows the chrome's
  `vwf_view` handlers to observe all of the actions for the
  document--not just the ones that occur after the chrome happens to
  load.

Closes #188.
Load the application chrome as a service instead of a file.

Instead of having the client parse the URL and guess at the application
name, load the `application.vwf.html` overlay using a fixed path
relative to the application root.

Since applications aren't required to provide an overlay, return an
empty result with status code 200 when the overlay doesn't exist.
Otherwise, the log will show an error for a condition that isn't really
an error.

Closes #741.