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

Conflicts:
	tardis/tardis_portal/templates/tardis_portal/ajax/experiment_description.html

Resolved:
	merged button styling change from master
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

Conflicts:

	tardis/tardis_portal/views.py
get_download_url shouldn't croak if there is currently no accessible replica
Use better names for some config and context parameters
Unit tests for download format/organization changes