Moved an import in an auth test; refs #23925.

This keeps tests/__init__.py from importing other modules and may fix a problem
with test discovery revealed in formtools tests on Travis CI.
Refs #23947 -- Fixed admin_views test execution order dependency.
Corrected test assertion from refs #21403.
Refs #23947 -- Fixed queries test execution order dependency.

Specify an id to avoid conflict with objects created in setUpTestData.
Fixed #23987 -- Made SQLite SchemaEditor always use effective_default().
Fixed typos in docs/releases/1.7.2.txt.
Fixed #23405 -- Fixed makemigrations prompt when adding Text/CharField.

A default is no longer required.
Refs #23947 -- migrations test operation fix

Refactored the way tables are droped to use SchemaEditor.