RFE: X-Broker-API-Originating-Identity support

[jim-minter]

Some brokers already expect to receive a X-Broker-API-Originating-Identity HTTP header on nearly every operation. At the moment the framework doesn't make it too easy to specify this in tests. More functionality for this (and maybe arbitrary HTTP headers?) would be good.

[leonwanghui]

IMO, this is related to a potential issue that the checker tool assumes brokers only support basic authentication, which means you would change the default way of authentication if you want to add X-Broker-API-Originating-Identity header.