Feature/get igaperson
Introduces get_igaperson_by_username and get_igaperson_by_personid.
Both methods take a set of field names as argument, which determines which api calls are done so that one does not have to fetch info one does not need.
The return a new model called IgaPerson modeled such that info related to a person is saved to various fields on that model, while info related to the accounts of the person are saved to IgaPerson.accounts as a list of IgaAccount objects.