Listview icon size scaling

[btigi]

Add ability to resize icons (in the listview mode) by holding down the Ctrl button and using the mousewheel.

Added a #define to use smooth frame resizing (rather than resizing based on the icon width).

Note: This line throws an exception when I run the project
_currentVD = Array.IndexOf(VirtualDesktop.GetDesktops(), VirtualDesktop.Current) + 1;
I've been commenting out the entire block during development, though I've left it uncommented in the commit as presumably it's working for everyone else.

[PinchToDebug]

1. Many thumbnails aren't fetched correctly and the fetching isn't async so it freezes the whole desktop.
   

2. The item's width is looking odd.
   

3. Resizing only works when the items aren't scrolling.

4. I don't know why it saves the icon sizes there.
   

5. #define smoothresize - seems unnecessary.

6. Thumbnails don't get fetched if its a folder

   if (File.Exists(path))
   {
   ....
   }

[btigi]

I can pick these issues up but it won't be for a week or two, though anyone else can feel free to improve this PR (which I think is a decent start on the feature) in the meantime.

Resizing only works when the items aren't scrolling.

Yeah, I don't really know how to resolve this one. I played around setting the Handled event on the parameter but couldn't get sensible behaviour.

define smoothresize - seems unnecessary.

Personally I find the current resize behaviour counter intuitive. It's obvious an icon won't fit in the additional space the user is created with the resize action, but it's not obvious why the window doesn't actually resize to the size the user wants. The most common application that displays icons, i.e. Windows Explorer, is probably something that most users are familiar with.