Check if it is possible to create device nodes in the work folder

Created by: ollieparanoid

We've had a few cases where the device node creation did not work. It would be nice if we check that during pmbootstrap init and tell the user what could cause this and what to do about it (use another location, link to a wiki page with details).

Possible causes:

Shared VM folder
NTFS folder?
Old versions of ecryptfs
maybe encfs

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information