remove service-point handling

Summary: stripes-core does not depend on the inventory Okapi interface; thus it must not contain logic related to data derived from this interface. 

Details: Service points leaked into stripes-core by parsing the response from /bl-users/login when its optional dependency on the inventory interface is fulfilled, but stripes-core itself does not depend on this interface and thus should not contain logic related to such data. Instead, the login response should be stored in redux and applications that do rely on inventory can use an event handler attached to the LOGIN event to retrieve that response and operate on it (e.g. UISP-32).

Note: This will be a breaking change because setServicePoints and setCurServicePoint are publicly exported.