Fixes a few issues with the default server configuration.
There were a few issues with the default values defined in the ProjectRazor::Config::Server
class (which are written out to the filesystem as a configuration file in the case where there
is no configuration defined yet for the Razor server).  Specifically, the default value for the
'mk_fact_excl_pattern' didn't include the 'memoryfree_mb' fact as one of the facts to ignore
(recent versions of Facter use this fact name instead of the old 'memoryfree' fact name)
and the defaults['mk_tce_mirror_port'] value is now used when defining the
defaults['mk_tce_mirror_uri'] property (instead of the, now undefined, @mk_tce_mirror_port
field from previous versions of this class).  With these changes in place, any new default
configurations output by Razor should be correct (to within an IP address or two)