Support fuse/mtpfs mounts (like tablets, phones) with the diskfull sidebar indicator

I used the following guide to setup my system for my tablet:

http://bernaerts.dyndns.org/linux/247-ubuntu-automount-nexus7-mtp

Obviously a PIA, but once it's set up, it works reliably.

All this change to Nemo really does is recognize these types of
devices as legitimate mounts, and allow them to be viewed as such.