Cleanup

Fix headers - remove duplicates and reorder to reduce future duplicates.
Remove unused model.
Add SIP Arrangement table

refs #6131

Add table to track SIP Arrangement in the database.  Schema still flexible.
Add dashboard syncdb to dev-helper script

Update recreateDB script called by dev-helper to run syncdb for the
dashboard.  Add new permissions for archivematica to run syncdb properly
(CREATE, ALTER, INDEX).
Set up dashboard testing fixtures

Add config for testing fixtures folder, and an initial test user fixture.
Add arrange contents view that reads from DB

refs #6131

Add view that queries SIPArrange table and returns the entries and
directories for Javascript file-browser.  Add test for that function.