Changes from $client -> $distro

There were a few places in brg where the distro-specific includes for
Bedrock clients were using "$supportfuncs/$client" instead of
"$supportfuncs/$distro", specifically, preventing list_release and
list_arch from working.
Ubuntu used abs path for sourcing Debian brg

Debian functions for brg were being sourced in Ubuntu's as
"/home/paradigm/.src/brg/debian". Adjusted to use $supportfuncs to allow
for proper functionality from Bedrock while still enabling testing.
Added CentOS support functions

This is has not been tested very much yet, use at your own risk.