clean up, clarify, and condense options in `main.py`

[ascourtas]

Currently, there are options in main.py that are not used or are redundant. Additionally, some just need more clarification in the help string.

• [x] Remove deprecated options, consolidate options as appropriate (ex: --epochs and --epoch, --aug and --transform, taking out --slices and hardcode it to 1)
• [ ] Improve help strings in argparse to describe the option, the use case/context in which the option used, and the default value if any
• [x] Adjust option names if they're specific to only a certain mode or process (ex: adding "hpo" to all of the HPO-specific options, adding "matcnn" to --version)

For more granular notes on options that stood out, see the April 7th meeting notes https://docs.google.com/document/d/1yYnpvj9rA-Dpbx051P8SkkTA4315Pp7fqnz08x3tsyA/edit#heading=h.ikz31eidp5ot

The issue #37 will address adding if/else checks in the code to warn the user if they're using a combination of options that conflict, or are unnecessary

[ascourtas]

@jimtjames I assigned you since you started this work this week, but feel free to reassign as necessary

[jimtjames]

Cleaned some of these. Will need to modify the MatCNN submodule as well.

[ascourtas]

@jimtjames can you clarify where we're at on this one?

[jimtjames]

Ticked the corresponding boxes! This is almost done.