Support sending force_text_type= in POST requests.
Review Request #6421 — Created Oct. 8, 2014 and submitted
POST requests now support force_text_type=, in order to force the text
to be of a certain type. This mirrors the ?force-text-type= argument in
The resources that support this have been updated to take this argument
in their supported field lists.
The "html" text type is also no longer set as saveable.
Tested manually and with my other changes.
Unit tests pass.