Call out that extra fields in requests and responses are allowed
Call out that extra fields in requests and responses are allowed

This change will make it clear that request and responses that
have HTTP bodies MAY have additional fields specified by the
sender.

Signed-off-by: Doug Davis <ff3bde741799c0eff815b83a54eda3fc494df54f@us.ibm.com>

servicebroker/servicebroker,servicebroker/servicebroker,servicebroker/servicebroker,openservicebrokerapi/servicebroker