Introduce mounting, fstab, autofs

Introduces the mount command and some of its options. Takes apart
an /etc/fstab file. Briefly introduces autofs and an
/etc/auto.master file. Autofs has a bit too many prerequisites to
be meaningfully covered here, but it is at least introduced with
an example, and discusses the chain of events during an automount.
Merge pull request #122 from nibalizer/mount_fstab_autofs

Introduce mounting, fstab, autofs