Provide a tool or PyFilesystem opener to support using as a FUSE filesystem

[mechanical-snail]

Provide a PyFilesystem opener, i.e. a URI scheme that PyFilesystem would use to represent the filesystem.

Providing an opener would allow dropboxfs to be used as a FUSE filesystem on Linux with PyFilesystem's command-line tools (using an example URI scheme):

$ fsmount 'dropboxfs://app_folder?token_key=foo&token_secret=bar' /mountpoint

Alternatively, provide a separate command-line tool (look at how PyFilesystem's pypi package does it) that acts as a FUSE filesystem mounter.