testing/factory: added MakeEnvironment helper to Factory

To support testing of multi-environment scenarios.
testing/factory: removed formerly accurate comments
Merge pull request #1201 from mjs/factory-makeenviron

testing/factory: added MakeEnvironment helper to Factory

To support testing of multi-environment scenarios.

Also removed some comments which are no longer accurate.

(Review request: http://reviews.vapour.ws/r/511/)