User guide for submitter/internally implemented was never published

[petertorelli]

Hi Guys,
Way back last year I wrote a large section in this document that explained the test harness. This was never published and the comments were removed when the code was re-written from the EEMBC layout to the new "submitter/internally implemented" structure. I've seen some bugs and questions related to lack of documentation, and I think would help to add this as a user-guide and update it to match the new code structure Nat implemented.

Peter