* Moved the PANEL_MAX_OUTPUTS define in 'lib/rdsound_panel.h' to
RD_SOUNDPANEL_MAX_OUTPUTS in 'lib/rd.h'.
* Added a 'RDPortNames' class.
* Added a 'RDCoreApplication::portNames()' method.
* Refactored rdairplay(1) to use 'RDPortNames'.
* Refactored rdpanel(1) to use 'RDPortNames'.
* Removed the 'RDAirPlayConf::portName()' method.
* Removed the 'RDAirPlayConf::soundPanelChannelName()' method.
Signed-off-by: Fred Gleason <fredg@paravelsystems.com>