Change trash function to follow osx naming convention

Changes the `osx` plugin's `trash` function to follow the file naming conventions used when trashing from Finder. 

For example, a file called `filename.ext` trashed at 16:42:04 will become `filename 4.42.04 PM.ext` to avoid naming conflicts if `filename.ext` already exists in the trash. A file `filename` with no extension likewise will become `filename 4.42.04 PM`.