Enhancement: Attribution/Reference/Link data for content blocks

[iandrosov]

OVERVIEW
Add a rich text field to content block to track source/referenced data related to any facts in the content -- give the user a way to track original source or reference materials related to the content where there was some analysis done to produce facts/stats or link to source materials. Ideally also copy this data when a content block is used in a grant so that it tracks the original 'source' data used in that grant.

ACCEPTANCE CRITERIA
* One or more fields to store data
* UI to edit/maintain content
* Extend 'Add block' functionality to copy field to grant

OUT OF SCOPE

BACKGROUND/REFERENCE