New proposed BaseVoltage instances

[natlefs]

We'd love to see usage of common reference data in the Norwegian IGM's, and the obvious place to go for this data seems to be here. But if we are to use the Telemark120 BaseVoltage instances for such a thing we will need some more of them to meet the sum of needs seen in the Norwegian grid.

A separate use-case we want to support is the ability to "squish" a messy set of BaseVoltages into these standard ones using a set of ranges. We'd apply this process to IGM's that Elbits work with internally as well as to our Nemo data products, and hope that other actors would like to do the same.

I'm setting this up as a draft with a few associated things to consider

1. Are the proposed nominal voltages sensible? (I've struggled to justify both 47kV and 50kV as nominal)
2. Does the proposed ranges make sense, and should they be included here?
3. Along with these proposed changes - should we toggle dataset ID's or versions, or consider adding a dcterms:modified ?

Appended is a table of the sum of proposed BaseVoltages with their suggested range (in V, the code uses kV)

Nominal Voltage	Floor voltage (inclusive)	Ceiling voltage (exclusive)
230V	140	300
400V	300	550
690V	550	800
1000V	800	1500
6kV	1500	8000
11kV	8000	14000
17kV	14000	19500
22kV	19500	26000
33kV	26000	42000
47kV	42000	48500
50kV	48500	58000
66kV	58000	80000
110kV	80000	117000
132kV	117000	180000
300kV	180000	360000
420kV	360000	600000
1000kV	600000	9900000