should add committee membership data from the new knesset API

[OriHoch]

expected outcome

this is only a suggestion, feel free to implement it another way

from knesset_data.dataservice.persons import PersonPosition
for person_position in PersonPosition.get_all():
    peson_position.PersonID
    person_position.CommitteeID
    # all other fields..
    
    # mk = Member of Knesset
    # this method should return the standard member id, like:
    # 901 = איציק שמולי
    person_position.get_mk_id()
    
    # given person_position.CommitteeId
    # fetch and return a dataservice.committees.Committee object
    person_position.get_committee()

relevant documentation and details:

• knesset data API documentation - https://docs.google.com/document/d/1FHqabNsYlSNyul1lArmnONLHnYGA4XQNMs3k-dPgUok/edit
• how to add a dataservice object - https://github.com/hasadna/knesset-data-python/tree/master/knesset_data/dataservice#how-to-add-a-new-collection-dataservice
• @davi17g is working on similar issue, have a look at his PR - added bills dataservice #8
• related knesset-data issue: Committee members data is wrong / not updated knesset-data#133

[OriHoch]

the basic data is there, but some follow-up is needed:

• write automated tests
• fix the is_current field boolean value
• add the relationship to committees (possibly just document it)