Implement method transforms

[Tratcher]

#444
Some servers only accept basic HTTP methods like GET and POST, not PUT or DELETE. Implement request method transforms like PUT -> POST.

• It would look a lot like the PathSet transform.
• Derive from RequestParamtersTransform.
• Modify RequestParametersTransformContext.Method

Related: Consider support for the X-Http-Method-Override header to preserve the original method. This would have to be a separate transform since headers are processed seperately.

[samsp-msft]

I’d like to see this one done as an extension - it would be a good way to prove if we have the right extensibility points?

[Tratcher]

It would be interesting as an exercise when we actually build those extensibility points (#60) to test...

[karelz]

Triage: Apparently happens to a few customers (sad), should be simple to do.