Allow/fix admin search for Dataset, Datafile, Replica and Location by 'id'
New django command for changing experiment ownership.
Another optimization for mirroring.  If the datafile is already mirrored, don't bother with the read-back-and-verify.
Defend against truncated files in the filestore causing put_file to lock up.
Implemented Grischa's suggested change for the new REQUIRE_* attributes
Fix for 1 bug and 1 issue in FilterInitMiddleware.  Plus a unit test!

The issue is that we no longer get a Dataset_File save when we've
successfully uploaded the file content (and verified).  That is a save
on the Replica.  So we weren't running the filters when the file content
became available.  This fix adds a 'post_save' signal on Replica which
runs the filter on the Dataset_File if the Replica is now verified.

The bug is a minor one in the way that filter parameters were configured
in the POST_SAVE_FILTERS setting.  If you had both **args and **kwargs, the
former were silently ignored.
Checkpoint
Completed and did some initial testing
Bug fixes and tidyups
Checkpoint of code to handle custom archive organizations
Checkpoint ... organization support mostly working apart from unit tests
Completed the unit test changes, and added some testing for 'tar' format
Added documentation and implemented 'filtering out'.  Also fixed a bug
in the way I was wrapping the mapper functions.
First cut at wiring up the new download stuff to to UI
Documentation tweak
Updated UI for download.  Better "download experiment" button & download selected datasets / datafiles now download in "default" org and archive type
Bug fix download in a dataset