Add rationale information to constraints

[samm82]

As mentioned in #1491, #3091, and #3187, we should have a way to add rationale information to constraints. This could be a source, a derivation, or potentially something else.

Not all constraints would have a rationale, so we would need a way to accommodate that. My immediate thought is to use Maybe, but I know we are trying to avoid that (#2677).

TODO

• Add the ability to store rationale information to ConstraintE (or create a new data type that allows for this?)
• Display constraint rationale, if applicable, beneath the relevant table (Input/Output Data Constraints).

[smiths]

Although it isn't part of this issue, we should make sure that the rationale information can also be added to assumptions. Actually the rationale will be added "outside" the assumption to justify that we can invoke that assumption. For instance, in projectile we assume constant acceleration. That is a mathematical assumption that the physics equations depend on. If we want to use these equations to solve a particular problem, we need to be able to justify that we have constant acceleration. That is, we need to be able to provide a rationale for invoking the assumption. In the case of projectile motion we can use the constant acceleration assumption because the acceleration varies very little by height. (We could quantify this if needed.)