[WIP] More Test Suite Improvements

Assorted things related to tests:

 - [x] the batch file is gone and replaced with a leaner, meaner Powershell script 
 - [x] if you've got a `OCTOKIT_GITHUBCLIENTID` and `OCTOKIT_CLIENTSECRET` defined (as well as your credentials), the build script will fetch a token from the GitHub API and set it in the environment variables
 - [ ] this token should be validated in subsequent sessions to ensure it hasn't been revoked
 - [x] some clown forgot to update his integration tests to actually follow a rule he specified in #243 
 - [x] document the changes so that contributors can get back to work
 - [x] removed all the namespaces for the integration test classes
 - [x] enabled some more tests

Test Plan:

 - [ ] no environment variables defined -> no integration tests run, see message
 - [ ] four `OCTOKIT_` environment variables defined -> create token, store in $env:, run integration tests
 - [ ] token + four `OCTOKIT_` environment variables defined -> check token, run integration tests
 - [ ] bad token + four `OCTOKIT_` environment variables defined -> check token, replace with new token, run integration tests
 - [ ] revoked token + four `OCTOKIT_` environment variables defined -> check token, replace with new token, run integration tests