Don't try to close the window when a mount goes away

Go to home instead.

https://bugzilla.gnome.org/show_bug.cgi?id=666985
Merged directory monitor solution, but stick with volume monitor for glib < 2.34

Merge commit '0852847e2613dbcebb4ed7f58e5b2aee3aa86a90' into nemo_master_merge

Conflicts:
	libnemo-private/nemo-file-utilities.h
	src/nemo-application.c
	src/nemo-pathbar.c
	src/nemo-window-manage-views.c
	src/nemo-window-slot.c
	src/nemo-window-slot.h