Some more tests.

- Changed the way URLs are generated/handled.  Absolute URLs will be
  used as is to trigger security restrictions if any, so that the user
  will be notified that something was wrong at the generation time.  Of
  course this won't help with what happens later, but users are going to
  use this however they like...
Added more tests

- Also unified the two sets of tests but run with two different layers.
Making this test model actually work.
With a demo to use the test main model.
Make the `pmr:` uri friendly for urljoin

- Whoops, it needed a headling slash to denote where the file path
  begins so that the normalization process can properly normalize
  relative links using a file on the root of the workspace.
Setup the demo model
The most basic integrated loader test.