Allow addPlay to specify index

[gilphilbert]

Enhance addPlay to allow the selection of a track index. Used as:

`io.emit('addPlay ', { list: [ { "uri" : "..." }, { "uri" : "..." } ], index: 1 });

Would add two tracks to the queue and play the second track.

[xipmix]

A couple of questions/comments:

• this would be clearer

                  if (data.index != undefined) {
                      index=data.index;
                  }

or even
if (data.index != undefined) index=data.index;

• Missing ; on this line?
  self.commandRouter.addQueueItems(tracks)
• too much Indentation on the line below?

[gilphilbert]

Thanks xipmix. This was taken from my dev machine, surprised it works with the missing semicolon - I missed that.

I've corrected the whitespace (as well as updating for 4-space indenting to match the rest of the file) and changed the if statement to include braces.

[xipmix]

This is indeed conflicting, I tried a test merge with 2488f38. It would be nice if github flagged such PRs in the summary list, I thought it used to do that. Do authors get a ping from github when their PR starts to conflict? I guess not.

Care to respin? Also I'm not clear how the variable e gets initialised now.

[gilphilbert]

Will respin, closing this PR