Start using a unified box command

Parse the command line arguments and forward them to respective
subroutines. Just the `./setup` side of things have been implemented
here.

Work done for GH-12
Move var.sh and ks.cfg

  * vars.sh -> etc/box.conf
  * ks.cfg -> etc/ks/centos65-x86_64.cfg
New switch to specify different kickstart file
New switch to specify different local config file
Add documentation for `box` command

A few manpages describing `box` command itself as well as its
configuration file `box.conf`. The man pages are written in mdoc
form.