Add prop/ref value search for datasets

[andebor]

We currently don't have a built in feature to search for specific property values in a datasets. Currently we solve this by piping the whole dataset to jq.

mim dataset entities stuff.Mydata --limit -1 --json | jq ' map(select(.props["ns80:my_property"] == "foo"))'

This can be very memory demanding for large datasets and quite unreliable. I propose that until we have a proper search to handle this in the backend, we add a command that will do more or less the same in cli. That would allow us to go through the dataset batch by batch, avoiding filling up the memory with temp entities.

It could look something like this:

mim dataset search stuff.Mydata --prop-filter ns80:my_property "foo"
mim dataset search stuff.Mydata --ref-filter ns80:my_ref "ns:60:bar"

I suggest that we also add a pterm progressbar output while searching. https://github.com/pterm/pterm/tree/master/_examples/progressbar