Entities support

Added user entities support.
You can redefine your entities for particular request using entities query field.

ApiAIPlugin.requestText({
    query: text,
    entities: [
      {
        name: "dwarfs",
        entries: [
          {
            value: "Ori",
            synonyms: [
              "ori",
              "Nori"
            ]
          }
        ]
      }
    ]
},
function (response) {
    alert(JSON.stringify(response));
},
function (error) {
    alert("Error!\n" + error);
});

See sample app for details.