Added Preferences Window & Account Upload support

I've added a Preferences Window (similar to the last project's), which has a functional Account Support tab.

I've also added my name to the "About" tab, which of course you can remove (I've kept the main repo URL and the main project's name (my fork is named swift2imgur))

I also wanted to report a bug: When you delete a screenshot (ex: from the desktop), the program crashes.

It would also be great enabling the "Delete after upload" option