Allensdk

- Refactored the schema for the ecephys copy utility to avoid raising an error when a previous output file already exists.

- python 3.8 compatibility
- CloudCache (the class supporting cloud-based data releases) is now smart enough to construct symlinks between files that are identical across dataset versions (rather than downloading duplicate copies of files).
- VisualBehavioOphysProjectCache supports user-controlled switching between dataset versions.

- Adds restriction to require hdmf version to be strictly less than 2.5.0 which accidentally introduced a major version breaking change

- This version marks the release of Visual Behavior Optical Physiology data! For more details please visit the: [Visual Behavior - Optical Physiology Project Page](https://allensdk.readthedocs.io/en/latest/visual_behavior_optical_physiology.html)
- update documentation to support visual behavior data release
- Fixes a bug with the dictionary returned by BehaviorSession get get_performance_metrics() method
- Adds docstrings to the BehaviorSession get_performance_metrics(), get_rolling_performance_df(), and get_reward_rate() methods

- changes name of BehaviorProjectCache to VisualBehaviorOphysProjectCache
- changes VisualBehaviorOphysProjectCache method get_session_table() to get_ophys_session_table()
- changes VisualBehaviorOphysProjectCache method get_experiment_table() to get_ophys_experiment_table()
- VisualBehaviorOphysProjectCache is enabled to instantiate from_s3_cache() and from_local_cache()
- Improvements to BehaviorProjectCache
- Adds project metadata writer

- Updates to Session metadata; refactors implementation to use class rather than dict internally
- Fixes a bug that was preventing Allen Institute Windows users from accessing gratings images