MinimalConformance100501 expected status code

[mikewatt]

The MinimalConformance100501 rule appears to expect an HTTP 415 in response to a GET request with unknown or unsupported format parameters in the accept header [1]. I don't believe the required HTTP response status code is stipulated in the OData spec, but a much more appropriate response code would be HTTP 406 [2], and this test should at least accept both.

We have run into this as we have a service (based on Apache Olingo) failing this rule.

[1]https://github.com/OData/ValidationTool/blob/master/src/CodeRules/Conformance/MinimalConformance100501.cs#L76

[2]https://tools.ietf.org/html/rfc7231#section-6.5.6