Bring in the testrunner/http server scaffold for better integration testing.

This brings in a copy of llmessage's llsdmessage testing server.  We run
a mocked HTTP service to handle requests and the integration tests run
against it by picking up the LL_TEST_PORT environment variable when running.
Add some checks and output to produce useful info when run in the wrong
environment and when bad status is received.  Later will add a dead port
as well so we can test that rather than use 'localhost:2'.