Interface Update

[knro]

Current device interface are implemented by multiple inheritance. I believe a better approach is required to simplify this. One method is to create an abstract interface and then subclass each interface to implement the standard ISXXX functions along with init/update Properties.

The default device maintain a vector of initialized interfaces and calls such functions accordingly so the concrete drivers do not need to explicitly call them like they do now.

Next comes the actual implementation of the functionality. For example, GuideNorth in guider interface must be implemented by the concrete driver. Should we require concrete drivers to register the callback? i.e.

guiderInterface->registerGuideNorth(std::bind(&MyConcreteDriver::GuideNorth, this));

Then when the internal code in guider interface needs to call this function, then it's already registered.

@pawel-soja @karlrees @eric-vickery @sterne-jaeger Please share your thoughts.