Update, document Ubercart 7 fixtures

Problem/Motivation

It's hard to modify the fixtures for improved test coverage because they're out of date versus what can be downloaded today.

Proposed resolution

Document the pieces necessary to generate the fixtures, and then update the fixtures.

Remaining tasks

• Document what is necessary to run the fixtures.
• Create a Drush Make file that itemizes the pieces necessary to build a local install.
• Update the current fixtures.

User interface changes

n/a

API changes

n/a

Data model changes

n/a