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
I suggest changing all the property names in this file that return `True` or `False` for visibility to be prefixed with `is_`. For example, change this to `is_view_all_link_visible`.