move all code into namespace QsExecute

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>
QtScriptActor to execute background QtScript tasks

QML WorkerScript allows to execute javascript in background
thread. QtScriptActor does the same except it also initializes
QtScript execution context. Also it has a bit different model of
interaction: to send message it also uses function with the name
sendMessage() but:

- it takes as parameter optional callback function executed
  asynchronously with the reply from qtscript handler

- return value of qtscript (set in the 'source' parameter) should be
  the function to be used to process messages from main declarative
  context

import Mer.QtScript 1.0
QtScriptActor {
    source : "somescript.js";
    function sendMessage(msg, onReply)
}

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jollamobile.com>