Request: In Satellite Tracker, allow AOS/LOS commands to use Satellite Tracker variables

[gvimlag]

Request:
According to https://github.com/f4exb/sdrangel/blob/master/plugins/feature/satellitetracker/readme.md
the "AOS speech warning" and "LOS speech warning" allow the user to use the following variables:

  ${name}
  ${duration}
  ${elevation}

Please allow the "AOS command" and "LOS command" (under both "Show settings dialog" and "SDRangel control") to also use these variables.
In addition, please add more variables. For example:

  ${name}
  ${duration}
  ${elevation}
  ${LOS}
  ${AOS}
  ${Range}

Use examples (under both "Show settings dialog" and "SDRangel control"):

  AOS command: /tmp/test.bash "${name} started at ${AOS} at ${Range} kilometers"
  LOS command: /tmp/test.bash "${name} stopped at ${LOS} at ${Range} kilometers"

[srcejon]

Implemented in above patch.