Only display current party memberships

[k-nut]

Right now the query includes all party memberships of the people that have the currently checked qualifier.

This means that if we get the result for the 17th period in NRW it will also include all parties that current members once where a part of. So if Politician A is in the Landtag for the SPD now but also used to be a member of the KPD we will show both parties.

This is also the reason for the single red dot in the example from the readme:

I am not sure what the best approach would be but we could for example check for all memberships if they have an end date and if so exclude those.