Implement searching on type and in collection.

Service can accept queries containing type and/or a collection id.
Add a custom json renderer.

Added adapters to a json_renderer to facilitate rendering
skosprovider.skos objects to json.
Reorganisation tests.

Reorganising the test suite so the tests can be placed in different
modules.
Added some functional tests.

Added a dependency on webtest and some (one) functional test.