(CPR-5) Move dmidecode from dependency to recommends

Previously facter had a hard dependency on dmidecode. This made the
debian package uninstallable on ARM based devices such as raspberry pi.
This commit moves dmidecode from dependency to recommends. In nearly all
cases dmidecode will still be pulled in, unless it can't be (as in the
ARM case).

Note this is a packaging change only.

Signed-off-by: Michael Stahnke <stahnma@puppetlabs.com>