* Refactors sending IPP request and handling errors thereof into sendIPPRequest()
* Adds dependency of IPP zgrab2 schema on HTTP zgrab2 schema.
* Refactors out trying to grab with multiple versions into re-usable function.
* Determines whether to output nil result in a concise and accurate manner.
* Refactors reading attributes present in IPP response to its own function. Calls that in Grab and augmentWithCUPSData. Formats code using Go fmt.
* Rejects successful non-IPP responses with protocol error. Reports HTTP errors.
* Removes circular dependency upon http zgrab2 schema.
* Changes name of objects to make IPP schema actually work.