/// This is the base class for all app global singletons
///
/// All global singletons are created/destroyed at boot time by QGCApplication::_createSingletons and destroyed by QGC::Application::_destroySingletons.
/// This is done in order to make sure they are all created on the main thread. As such no other code other than Unit Test
/// code has access to the constructor/destructor. QGCSingleton supports replacing singletons with a mock implementation.
/// In this case your object must derive from an interface which in turn derives from QGCSingleton. Youu can then use
/// the setMock method to add and remove you mock implementation. See UASManager example usage. In order to provide the
/// appropriate methods to make all this work you need to use the DECLARE_QGC_SINGLETON and IMPLEMENT_QGC_SINGLETON