Map out data notifications in the rust api

[greaka]

What is the feature you'd like to have?
BNBinaryDataNotification would allow me to subscribe to data events emitted by BVs.

Is your feature request related to a problem?
I would like to write plugins using that api.

Are any alternative solutions acceptable?
Lot's of ideas on how to implement it, but the quick and easy one is probably preferable at this time.

Additional Information:
A quick and easy solution would be to expose the notifier as a trait and on callback init/register check for fn ptr equality for impls compared to a dummy struct to only subscribe to what's implemented.