Clean up create_*_datastream tests. B-b-b-b-b-bonus-s-s-s-s-s:

NEW CUSTOM RSPEC MATCHER!!!

Use match_xml_except when you want to compare two XML strings, but
ignore a specific element. The motivation was a file access time
element that changed each time the XML was generated, so the fixture
XML could never match the test XML.

Use like so:

expect( @m.datastreams["ARCHV-TECHMD"].content ).to match_xml_except( jhove_xml, 'date' )

The matcher still needs work though. Plus it's ugly.
Merge branch 'refactor_uploads' of github.com:nulib/dil_hydra into refactor_uploads