categorizing metrics in visualization frontend instead of having type menus

[bonesoul]

So we have menus there with types listed.

Is it possible to instead categorize them by assigning a metric a category when we initialize it.

I know that we can create a metric for given type T, but i have multiple instances of that type which i would like track seperately.

somewhat related to #10 as at first hand I though of handling them in different registries, but I don't know if different registries are possible.

[etishor]

I've marked this as an enhancement and i'll leave it open until proper metric "categorization" or metric "sets" will be implemented.