gossip: add histogram calculation to gossip_load
gossip: improve (debug) console output of load_info
gossip: Add gossip_load to type_check_SUITE

Also add type checkers and value creators to gossip_load and refactor gossip_load
according to the results from the typechecking.
gossip: refactor setters and getterns in gossip2
gossip: Add gossip2 to type_check_SUITE

Also add type checkers and value creators to gossip2 and refactor according to
the results from the typechecking.