Make Request status not required, give default. #62176126

Per [story 62176126](https://www.pivotaltracker.com/story/show/62176126).  PBC Request import needed to mimic modal behavior, which does not make creator give a status, but instead defaults to Draft.

`StatusColumnHandler` is updated to follow `AssigneeColumnHandler's default-assigning behavior, which must override `go_import()` to ensure that a blank `None` entry for status still triggers the default assignment.

Template updated to reflect behavior.