[HPT-153] Start testing for linkage rules
Add siblings validation and fix the test to detect it properly
Script to purge all non-system objects from a Fedora
Flesh out test for required siblings
Add insertion test.

I thought we could use validation support much more than turned out to
be possible.  What I learned:  validation can't refer to other
ActiveFedora objects or things get tangled.

I also had to install a bypass switch in #save so that it can
recursively #save the siblings when they must be modified.  There's no
way for the tests that I moved from validation to work for both 'save's.
add delete test
Clean up tests, make link presence checks more rugged
Validator must account for this page being the one existing page
When updating a Page, sibs should point to this Page, not each other
Merge pull request #31 from mwoodiupui/HPT-153

[HPT-153] Pages belonging to a paged object should form a single connected sequence
Merge remote-tracking branch 'upstream/develop' into develop
Merge branch 'develop' into hpt-152
Fix nil last page detection after page deleted.