Create groups for measurements by type to filter the C37 packet

[pesap]

Here are some example of queries that people could do:

• get all the voltage angle and magnitude measurements,
• get all the frequency measurements,
• get all the analog measurements,

[micahpw]

I think we can add some logic and a few http endpoints to return the channel names by the following:

• All Phasor Channel Names (and whether they are in polar or rectangular coordinates)
• All Frequency Channel Names
• All Analog Channel Names
• All Digital Channel Names

Then you can use the POST method in the /data endpoint to pass a list of channel names to return.

The other option would be separate endpoints like /phasors and /analogs to return all columns in those categories.