Initial Main Window Implementation

The instance and running of the CommandLine class was moved from the main function to the constructor of MainWindow.  A flag was added to the MainWindow class to indicate when the GUI is active (along with an access function).  If the command line instance reports that the arguments have been processed, this flag is set to false.  Otherwise (later), the GUI is setup and this flag is set to true.

In the main function, after the MainWindow is instanced (as a local variable), if the GUI is not active, a value of 0 (indicating no error) is returned.  It is not necessary to have a single shot timer to force the event processing loop to exist immediately - simply returning before starting the event loop is sufficient.

The MainWindow class definition starts with the Q_OBJECT macro.  Essentially this allows the use of signals and slots, which is a mechanism used by Qt to allow classes to communicate with each other.  More on this later when these get implemented, but for now, the MainWindow class does not contain any of these, but will as the GUI is developed.  Details about how these Qt GUI files are built with CMake in the next post.