Merce Installer/Configurator

We need to modify the Merce installer in the following ways:

• The installer will be separate from the configurator. The installer
  will only install packages, but will not configure any of them. It
  will not have any UI at all... it'll only show a tidy progress bar,
  do its installation job, and finally ask "Start the configuration
  process? (y/n)"

  If the PSG engr says "Y", it'll exec the configurator. If "N", the
  installer will quit.

  During our current Merce installation process, some things can only
  be done once, and others can be done multiple times. For instance,
  installing RPMs can only be done once (unless you uninstall first).
  But changing the domain name of the server can be done multiple
  times.

  The new installer will do (i) everything that does not require any
  human input, and (ii) everything that can be done only once. If
  something can be done multiple times and requires human inputs,
  it should go to the configurator.

  The new installer will install the new configurator on the server.
  After the installation process, the Merce CD should be removable if
  the engr wishes. The configurator can be run from the server's HDD,
  just like vmware-config.pl

  The new installer should leave the server in such a state that if
  the engr reboots it after install but before config, the server
  should not report any errors. (Its services may not be usable, but
  that's not important.)

• The new configurator will display the same CUI as the current
  installation script. It'll ask the same set of questions in the same
  sequence, and will configure the back-end services.

  The key thing that the new configurator must do (which the current
  one does not) is that it must be runnable multiple times. And when
  it is run a second time, it must prompt the engr with the old values
  of each question, so that the engr can just keep hitting Enter for
  all questions other than the one or two that she wants to change.