Added some basic resource URL tests, and fixed a bug that these exposed,
that the internal shallow asset locations within deep asset locations
were still discoverable using the BRJS locator methods, leading to
problems.
Removed a test that can no longer work now that we've removed the old
css tag handler.
Created a ResourcesAssetLocation class that can be responsible for
modeling theming, since themes are now a plug-in concern rather than a
model concern.
Added a test with a URL that refers to a parent directory, and fixed a
bug that this exposed.
Updated BRJSConformantAssetLocationPlugin.getBundlableNodeThemes() to
take into account the recent introduction of ResourceAssetLocation.
Changed the content paths used by the css resource plug-in so that they
match it's request prefix and don't use the same suffix as used by the
old bundler. Also modified how we access the theme asset locations,
making use of the new ResourcesAssetLocation class.