This change removes a bunch of things which are deprecated or no longer

needed:

The datagrid and integrations apps had old templatetags files that

  just raised warnings about their deprecation.
We had a number of backports of newer django functionality to allow us

  to maintain compatibility with Django 1.6.
We had some stuff that provided compatibility with the importlib

  module for Python versions that we no longer support (3.4 and below).
The old basictag decorator has been deprecated for a long time.

Ran unit tests.