Refactoring
* encapsulated position timers start/stop
* only start interim position timer when connected
* use Q_FUNC_INFO for Q_ASSERT_X
* interim pos. interval as const values
* private VatlibQScopedPointerDeleter (slack discussion)
Instead of enabling fast position updates via context methods, the
settings API will be used instead. This also allowed to move the timer
into CNetworkVatlib instead of CAirspaceMonitor. The only necessary thing
was to regularly update the receiver callsign set.
refs #677
