ISMN fixtures / settings

[wpreimes]

There is a "number of stations" field in the networks fixture, but this depends on the version of the ismn data. What is it used for?

[wpreimes]

Apparently nothing, we can remove it I guess, Same applies to the "country", which doesnt make much sense to have in the fixtures.

[wpreimes]

• Remove the number_of_stations and country fields from the networks fixture.
• Make variables depend on versions, not datasets. Variable names can change between versions.
• When multiple variables are available sort them by their depth (consider adding varible depth info), default should be the surface variable
• ALL ISMN stations in all networks should be activated by default, we have the FRM filter now.