Remove macOS/iOS specific implementations for public classes

A few iOS/macOS implementations have their own public class implementations (e.g. QLowEnergyService)

• Removes duplicated code
• Likely due to Objective C specifics -> needs investigation. Mainly due to osx-specific private header  files containing Objective C entities, which will fail to compile when included in *.cpp file. Working this around is possible, albeit a bit ugly but is still better than code duplication.