Updated test cases w.r.t to review meeting with Peter Walsh and @dnahodil.

Broadly:

* changed application of "protection" to be at the project level, rather than at the release level (as this is what the policy actually states);
* added explicit test cases for filtering (as this has been the source of some bugs in the past).
Refactored test-cases using scenario outlines.

This hopefully makes the tests more readable and easier to change, whilst providing better and more explicit coverage.
Merge pull request #96 from aodn/protected_releases_tests_update

Updated test cases w.r.t to review meeting with Peter Walsh and @dnahodi...