Speed up the tests.
Added general upgrade doc.
Modifications to the test suite to make it faster.
Support more rows in the bibliography.
Create a bibliographical item with a reference_title.
Removed extraneous tags.
Removed leftover print statement.
Support dependencies on .less files.
Use the DataTable code for inserting references.

The same DataTable code used for editing reference titles is now used
for inserting references in the text.
Removed the old code that has been superseded by DataTable.
Improved the editing of bibliographical references.
Dealt with some race conditions in the tests.
Added a test to make sure fresh objects are not refreshed.
Use an item's pk instead of the item_key for identification.
Don't present the add custom text menu if there is text already.
Removed old obsolete documentation.
Initial support for visible absences.
Added filters to the admin interface for changes.
Various placeholder fixes.
Made antonyms, cognates and conceptual-proximates mandatory.

They also now take <btw:none> if there is nothing in them.