This makes it much easier to apply to other projects.

Fixes to doc tests infrastructure:
* Fix comparing lists. Was totally broken.
* Fix order of actual vs expected parameters.
* Allow multiple `// TESTRESPONSE` lines with substitutions to join
into one big list of subtitutions. This makes lets the docs look
tidier.
* Exclude build from snippet scanning
* Allow subclasses of ESRestTestCase access to the admin execution context