WL-3156 Add test isolating behaviour

The locations and categories appear to be acting inconsistantly.
WL-3156 Fix code when fetching categories

Not only was the code in `getAllCategories` doing the wrong thing, it was
interfering with the cache for `getAllLocations`.

I have changed the code to match the format in `getAllLocations`.
WL-3156 Add test scope to test dependencies

We introduced some test dependencies so make sure that they have the test
scope in the pom file.
Merge pull request #30 from ox-it/WL-3156

WL-3156 Locations and Categories live in harmony