In preparation for upcoming changes for posting review requests, this

change splits out the very-complex field-building from post_request()

into __build_new_review_request_data() (for building field data for

new review requests) and _build_review_request_draft_data() (for

setting draft state).
These are now fully tested, thanks to the new command and API testing

infrastructure. This has unveiled a few tiny slaws, such as

bugs_closed being built in random sort order (now fixed) and

text_type being used instead of field-specific *_text_type fields

for draft fields (not fixed, but may be the cause of some obscure bugs

we've seen in the past).

All unit tests pass.
Manually posted several changes for review (including this one).