GCS/TelemetrySchedular Allow zero period updates

This makes the object not update at all but it is easier than changing
the updatemode
GCS/TelemetrySchedular Fix fixed row geometry issues
GCS/TelemetrySchedular Add option to hide objects not present on hw
GCS/TelemetrySchedular Only update or save changed objects

and if present on hw
GCS/TelemetrySchedular Add default extension to saved files
GCS/TelemetrySchedular Sort objects by name
GCS/TelemetrySchedular Update headers
GCS/TelemetrySchedular Fix headers and deleted debug statement
GCS/TelemetrySchedular Added doxygen to dataModel_itemChanged
GCS/TelemetrySchedular Fixed applySchedule doxygen
GCS/TelemetrySchedular applySchedule improve readability
GCS/TelemetrySchedular fixed "if" statements style
GCS/TelemetrySchedular added doxygen to fixGeometry function
GCS/TelemetrySchedular hide objs not present on hw by default
GCS/TelemetrySchedular added an empty item to the shedulelist combobox

If the user forgets to set the choosen item on the combobox a message
will popup with a warning.
Merge pull request #1261 from guilhermito/telemetry_schedular

Telemetry scheduler enhancements