[Operations] important/globaltopk + filters

[nfelnlp]

Created from #25

Right now, globaltopk only operates on a fixed set of pre-computed global explanations. It is only possible to use important on the whole dataset or on a specific class ({classname}).
If there's a way to efficiently compute them on other temp_datasets, we can combine this operation with different filters.

prompts/work_in_progress