New annotation client

[Anastasia Macmood]

A new annotations client is available from 1.22 effectively deprecating annotations in old client.

New annotations client provides functionality to annotate charms as well as environment, machine, service and unit previously done through our old client.
New annotations client also supports bulk calls.

For the SET annotations call that looks similar to this:

......{
            "Type": "Annotations",
            "Request": "Set",
            "Params": {
                 "Annotations": {{
                    "Entity": a, "Annotations": pairs1
                  },{
                    "Entity": b, "Annotations": pairs2
                  }}
}}......

corresponding GET annotations call may look like:

......{
            "Type": "Annotations",
            "Request": "Get",
            "Params": {
                 "Entities": {{
                    "Tag": a},{
                    "Tag": b}}
}}......

Returning

{
    "Results": {
          {"Entity": a, "Annotations": pairs1, "Error": nil},
          {"Entity": b, "Annotations": pairs2, "Error": nil},

    }

}

Note that where SET call returns an error, Error in GET call return is params.ErrorResult.