Restructure NumericAssessment JSON

While working on #1299 some inconsistencies were found in how NumericAssessments treated their children between the editor and the viewer, particularly when trying to extract out duplicate code between Numeric and MC Assessments. In a discussion with @zachberry a logical structure that could be consistent between Assessments was decided as follows:

(Note: The PR for #1299 introduces the AbstractAssessment chunk, which is designed to maintain Abstract sub-components that can be re-used between Assessments)

Each Assessment should have a children array of abstract Choice nodes Each Choice node defines its score (currently 0 or 100) and has 1 or 2 children The first child is an Answer node, that implements behavior specific to the assessment The second child is an optional abstract Feedback node that holds content chunks to explain the choice

The Assessment can then implement specific behavior on how to score a submitted answer, based on its child choices (ergo: -once we do validation - a NumericAssessment could decide that must-meet-all could be in effect, and so the input would have to meet all correct validations and not meet any of the incorrect, similar to the multi-select MCAssessment)

The PR for #1299 implements this design pattern for the editor, but the viewer still needs work.

[x] In the ObojoboJSON, NumericAnswers are stored as the numericChoices attribute on the NumericAssessment, instead of as a children array.
[x] Feedback nodes are stored as an attribute on each of these numericChoices, instead of as a child in a Choice node.
[ ] The viewer has duplication between ReactComponents for MCFeedback and NumericFeedback
[ ] The XML parser could be consolidated to use one feedback, and to make choices consistent between Assessments

ucfopen / Obojobo

Restructure NumericAssessment JSON #1313