Better user experience for trashing token images

[samcf]

There's a few issues with throwing token images in the trash currently...

• Hosts can't throw token images into the public trashcan, its a bug.
• Theres no reaction to dragging a token image over the trashcan so its not clear that dropping it in there will do anything.

In general it should be more obvious what will happen if you drop a token image into the trashcan.