Add option to not minimize to tray

It would be nice to have the option to not minimize the wallet to the tray when hitting the close button. I have poor internet connection so I don't leave the wallet open, and it a very slight annoyance to have to hit close, then right click on the tray, and hit exit.

I repeat, this is a very minor issue, and only if it is easy to implement in a non-cluttering way would I suggest it happen.

Thanks for all the work, devs.

[quangvu3]

We could not add the option for the latest release but you can see it at LITE wallet now ;)