default 'extension' in px.conf

[petersilva]

The global configuration file, px.conf
should contain the default extension for
receivers (or filters.)

one should be able to use -NAME (as in the name
of the rx or fx doing the naming... )as so that
our CMC default, for example, would likely be:

extension -NAME:-CCCC:-TT:-PRIORITY:Direct

That would remove a line from almost all of the
circuit connections (since they almost all use
this setting.)

was: https://sourceforge.net/p/metpx/feature-requests/23/