Sanity tests for Consumer Pages

This PR is for issue https://github.com/mozilla/marketplace-tests/issues/524

Tests are strengthened/modified, new tests added to address https://moztrap.mozilla.org/runtests/run/57/env/112/ list with sanity tests
This property is called `apps_count` but it does not return a count, it returns a collection, and then the calling code has to do a `len()` on the result. This is both confusing and inefficient. This method should be changed to return a count, not a collection.