Supports installation of either an xfce or an lxde desktop environment.
For now use B as identifier for INSTALLER_CD in contrib/testingcds.
Includes a framework to manipulate the isolinux configuration for x86 so
that a user can select which desktop he wishes to install.
For now use A as identifier for INSTALLER_CD in contrib/testingcds;
we should probably switch to a double digit scheme post lenny or
even generally rationalize the use of INSTALLER_CD.