Update Problem Schema

This is a message UpdateProblemSchema that lets the SME via TA3 communicate to TA2 what the problem is. (Perhaps there are also uses in the TA2->TA3 direction?) Although not a part of the present September evaluation, this is likely a part of future tests, and outside of evaluations, in the field, the SME may need to communicate the problem they are trying to solve. This message lets the SME set (or overwrite) pieces of the problem schema, while forcing these messages to be valid within the problem schema definition (as of version 2.12).

Additional changes to the enumeration include adding comment annotations for clarity of some values, and the addition of an UNDEFINED value to fields where the task at hand might not yet be defined as discussed in #8 (closed)