Align parsing of the req parameter with VCL and petridish

[tripodsan]

the req param is currently parsed as JSON. as mentioned in adobe/helix-cli#126 this might change.

[trieloff]

And in adobe/helix-cli#126 what is req.params here is passed as params request parameter there.

[tripodsan]

currently the pipeline gets already the dissected payload/action, as #7 (comment).

the openwhisk params.req is the encoded external request, and will become payload.request.
the openwhisk __ow_* is the internal request, and those properties become action.request

[trieloff]

I don't think we can effectively encode the entire request and put it in params.req because:

• generating JSON in VCL is error-prone
• most of the interesting stuff (headers) are already passed in __ow_headers anyway

But we can have

• one route for headers (through __ow_headers, to be put into payload.request.headers)
• one route for params (through params.params (url encoded), to be put into payload.request.params)
• one route for method (through params.method, to be put into payload.request.method)