Files deleted by SF should optionally go to recycle bin

[JonathanLydall]

C# seems supports sending files to a recycle bin quite easily: https://msdn.microsoft.com/en-us/library/ms127976.aspx

We should probably make this optional, either through a user option, or tick box at somewhere like the bottom of the "Changes" window with something like "Do Not Use Recycle Bin".