Update jsonrpc2.0/jsonrpc-request-2.0.json

Added number in place of integer to the allowed types of the the id field.

Updated notes with more detailed references in the spec.

Comments welcome, but that should bring it more into alignment with the current spec. :)

Is the goal here to reflect the spec exactly, or also to include the recommendations into the schema? 
Merge pull request #3 from mpcm/master

Updates the request object schema, and a question about intent.