.. in order for it to work in the context of flow control with hardware serial

added pinMode declaration for the RTS pin..

This allows a pointer to an object to be passed in while registering for callbacks. In turn, when the callback is invoked, the pointer will be included. This allows an instance added information, including an instance handler, for the more C++ types. This pattern is similar to the pattern followed in POSIX for thread creation.

Need to double check to see if system_events can only happen one at a time.

Will change when deprecated methods are removed.

Updated the GATT calback mechanism to separate setting the callback function pointer and enabling attributes. This is a cleaner method in the callback context world.