Gentoo:  Second attempt

All of the targets have now been updated using the croagh framework.  Bootstrapping and preparation works properly.  This has not been tested on ARM hardware.  I have made an overlay that contains X.org related packages that crouton relies on (xprintidle, and touchegg and its dependencies.)  Although they are not technically "releases," the script can install either Gentoo or Funtoo when specified with the -r flag.