Remove "jsonrpc" version and replace it by "gsp_version"

[jeromeetienne]

gsp.io.json is producing json file with the mention "jsonrpc": "2.0" but we are producing json not jsonrpc.

• This pull request remove the "jsonrpc" to avoid confusion
• it adds "gsp_version" : "1.0" to help keeping track of the json format we use
• based on json command output produces invalid jsonrpc ? #11

[rougier]

Not fan of "gsp_version" but ok.