Long term code updates

[ndiamant]

• Update tests so we actually run them.
• Tests should include linting and performance comparisons.
• Important code like TensorGenerator should have thoroughly tested properties even for multiprocessing, e.g. output batch values should match the hd5 they were read from.
• multimodal_multitask_worker should be simplified. Take in a batch post processing function and a path generator function so it doesn't have to handle siamese and mixup logic and whatever other new logic we'll want to add. In progress in Nd breakup multitask worker #77.
• Make names like tensor_maps_in consistent across functions.

[lucidtronix]

• consistent use of underscore and dashes in TensorMap names
• Type hints and documentation on all public functions
• Deprecate default_tensor_from_file
• Handle missing datetimes and datetimes as tensors cleanly