Move filter_by_ctnr logic from view to model
Filter key-values by ctnr
default ctnr filtering for DNS objects, plus View objects
Make filter_by_ctnr more consistent
add filter_by_ctnr to interfaces
select related systems in get_related_systems
Patch to #288 to fix broken view tests
Merge pull request #355 from murrown/fix_get_related_systems

Optimize get_related_systems
All tests pass, queries optimized.
Merge pull request #310 from murrown/more_filter_by_ctnr

More filter by ctnr, more stuff is filtered. Fully functional. All tests pass.