Add partial order and other options to Parsons in assignment builder

[ascholerChemeketa]

Currently the assignment builder does not support some options for Parsons problems:

1. Partial order grading
2. Code to be prepended/appended after completion to make runable

Partial Order
Sample:
https://runestone.academy/ns/books/published/PTXSB/parsons-exercises.html

PTX source:
https://github.com/PreTeXtBook/pretext/blob/0a7d187aa0a6ac9272c0993f60e8e2b9342cf89b/examples/sample-book/rune.xml#L3021

UI for this could be tricky. I could see something that just let's user draw connections to show dependencies and makes up identifiers based on those that the user does not control.

Runable

Sample:
https://runestone.academy/ns/books/published/PTXSB/parsons-exercises.html#parsons-with-executable

Source:
https://github.com/PreTeXtBook/pretext/blob/0a7d187aa0a6ac9272c0993f60e8e2b9342cf89b/examples/sample-book/rune.xml#L3103

Key here is the addition of program-preamble and/or program-postamble. Maybe a single page towards the end of the wizard with a checkbox (default off) to turn on executable mode (whether to allow/emit the text) and two text fields.