removed std::chrono usage from the application. The std::chrono library is cumbersome, and although you gain a known unit for a value, it can be incredibly convoluted to work for. In pingnoo now, if a time duration is shared as an integer, it's milliseconds. As a double, it's seconds, unless otherwise specified.
fixed issues with threads mixing std::thread and QThread, this causes problems with thread exiting. Fixes #77
fixed: Previous ICMPAPIPingEngine changes made to support singleShot moder equired further work as it was assuming that the engine had been started, with the singleShot changes introduced this is not true, a ping engine can be created and used without requiring a transmission thread (i.e it's a blocking call)