Fix sweep start/stop freq limits
SWEEP_CONTROL: implement main slots, needs testing

Implemented slots for carrierMode, etc. but not sure if these
will work properly. Needs testing.
SWEEP_CONTROL updates state properly on start
MarconiServer: create "hidden" ver of all settings

Settings are not accesible from within the server, because a context
cannot be passed in. Creating non-setting methods, and then calling
those from within the settings, makes all functionality accessible
to the server, with only settings available to the client.
SWEEP_CONTROL: ready to test CarrierMode button

All other buttons should not cause problems.