Address NWB Behavior Ophys feedback

[wbwakeman]

We received feedback from PyNWB on our Behavior ophys extension. This is necessary to get resolved before we start creating behavior-only NWB files, and adding new data to Behavior Ophys NWB files.

https://app.zenhub.com/files/35236880/9e76daa9-354f-4cb2-8275-673c842a9ff0/download

Need to address Extension and Validation issues.
Need to discuss and decide which of the best practice items to take on, also based on difficulty to implement.

Validation:
Create another NWB file based on these changes and send it back to Ryan and Ben