adding rpm package and errata profiler applicability functions according to the new design
incorporating minor fixes from the pull request review
adding a couple of the previously removed functions to errata profiler since they are being used by functions installing an errata
updating profiler mocks for newly added get_repo_units conduit function for applicability
adding and updating rpm and errata profiler unit tests for new applicability functions
Merge pull request #275 from pulp/skarmark-applicability-performance

adding rpm package and errata profiler applicability functions according to the new design, updating profiler mocks accordingly and unit tests