add "quality" indicator(s) to ratings proposals and limits provenance

[catkins-miso]

As discussed in #124 there is definitely utility in indicating how a rating was determined.

In the ICCP world we there is a Quality Class called "Current Source" attributes are telemetered, calculated, manual, and estimated.

A natural mapping of these Source value for ratings exchange would be:

ICCP	TROLIE
telemetered	DLR
calculated	AAR
estimated	Recourse Rating / time-bound static rating
manual	Operator Override

I'm invoking ICCP here because I want to propose that we use the ICCP values for this indicator in TROLIE but maintain in the spec a canonical mapping to the kinds of ratings that are exchanged in practice.

I think the proper names in the TROLIE column may evolve in their meaning over time, but I think from a compliance / auditing perspective its the attributes in the ICCP column that are important. To be clear the use cases we're trying to support here are being able to determine when we need to document a variance as well as promoting operator awareness. We also want to have a consistent mapping from traditional OT (ICCP) into TROLIE, since many grid operators will be mixing the two.

[catkins-miso]

Use cases:

• DLR fallback to AAR transparency.
• Split DLR / AAR implementation--RC needs to know the difference to ensure compliance. We don't explicitly define a ratings obligation in the spec, but it would evolve to support DLR vs AAR distinctions.