Reingest support

[Hwesta]

Changes related to METS changes on reingest. Related to artefactual/archivematica#391 This may be broken into multiple PRs later.

• Sort amdSecs and dmdSecs by ID
• get_file takes **kwargs to search on multiple attributes
• Improve parsing - don't set CREATED or STATUS, get replacement relationships for dmdSecs,
• Add MDWrap OTHERMDTYPE to metadata add contstructors
• Allow pre-created amdSecs (for compatibility with old ways of creating amdSecs, notably createMETS2 in Archivematica)
• FSEntrys no longer require path or label, which means the FLocat and structMap/div are optionally generated.
• techMD can be superseded
• Fix GROUPID parsing
• Update tests

[jhsimpson]

I ran the tests successfully, and tried the tool at the command line, and looks good to me. I'd like to see more documentation, I am still not entirely sure how to use all the new functionality provided by this PR, but the docs were a bit skimpy to start before this PR, so asking for more might be out of scope.

:+1: