[Mediacontroller] added subtitles feature and related ability

[Mediacontroller] added subtitles feature and related ability

[ACR] http://suprem.sec.samsung.net/jira/browse/TWDAPI-230

[Verification] Code compiles without errors.
Basic test in chrome console works properly.

/// 1. adding command listener
var mcServer = tizen.mediacontroller.createServer();
mcServer.updatePlaybackState("PLAY");
var changeListener = function(enabled, clientName)
{
    console.log("Subtitles mode change requested to: " + enabled + " by " + clientName);
    return new tizen.mediacontroller.RequestReply(new tizen.Bundle({"message": "Not allowed"}), 13);
};
watcherId = mcServer.subtitles.addChangeRequestListener(changeListener);

/// 2. checking NotSupportedError when sending without enabled ability
var mcClient = tizen.mediacontroller.getClient();
var mcServerInfo = mcClient.getLatestServerInfo()
var enabled = true;
mcServerInfo.subtitles.sendRequest(enabled,
    function(data, code)
    {
      console.log(
          "Server replied with return data: " + JSON.stringify(data) + " and code: " + code);
    });

/// 3. register listener for mode changes (client side)
watcherId = mcServerInfo.subtitles.addModeChangeListener(function(status)
{
  console.log(mcServerInfo.name + " server subtitles mode changed to " + status);
});

/// 4. change the value of subtitles (should trigger listener from point 3)
mcServer.subtitles.enabled = true

/// 5. enable ability of server
mcServer.abilities.subtitles = "YES"

/// sendRequest again (should trigger listener from point 1)
mcServerInfo.subtitles.sendRequest(enabled,
function(data, code)
{
  console.log(
      "Server replied with return data: " + JSON.stringify(data) + " and code: " + code);
});

/// 6. register ability change listener and trigger the update
var listener =
{
  onsimpleabilitychanged: function(server, type, ability)
  {
    console.log(type + " ability changed, server name: " + server.name + ", ability: " + ability);
  }
};
mcClient.addAbilityChangeListener(listener);

/// call updates to trigger listener
mcServer.abilities.subtitles = "NO"
mcServer.abilities.subtitles = "NO"
/// Listener should be triggered once

Change-Id: I00ad78a44b696a7d885d13499af77cf762e54c7e