Fix h5py issues, hydra compatibility, YAML config, and support for DataFrames/CSV files

[felixp8]

• Remove related packages from README
• Introduce H5Reader object to avoid persistent read file handles at the mercy of the garbage collector that may interfere with subsequent writes/extends.
• Switch from saving _meta.yaml as JSON to using YAML, while still supporting legacy JSON reading
• Avoid treating dunder attributes (with format __*__, e.g., __file__) as normal keys for attribute access, for compatibility with hydra instantiation
• Save/read pd.DataFrame objects as CSV instead of arrays
• Introduce single-threaded SWMR test that reproduces past h5py file lock issue but is fixed with H5Reader changes

[lappalainenj]

I really like the changes and enhancements! Minor comments below