converge Split APIs with Mixed and Draft
more split_draft methods
Corrected diff between 0K and 0 C
Merge pull request #4482 from edx/markhoeber/documentation/doc-666

Corrected diff between 0K and 0 C
ispublic is in active use by Stanford.
split create_item and create_child out as separate methods
Merge pull request #4488 from edx/christina/ispublic

ispublic is in active use by Stanford.
Merge pull request #4381 from edx/nimisha/split-converge-api

Nimisha/split converge api
Studio: corrects new course field tip copy to reflect what provided course values cannot be changed later
STUD-2001