Merge new model and config structures, CRUD functions

[neal-logan]

• Project Structure: Extracted hard-coded information about gestures to .json files in configs folder: gesture-index mappings, gesture-action mappings, and defaults for each. Moved paths for models, data, and configs to environmental variables for coordinate; see .env.example. Moved raw hand landmark data to .csv format for maximum flexibility in data folder.
• Model Features: Added left/right handedness to feature set. When added to 21 landmarks * 3 dimensions, this brings us to a nice, round 64 dimension. Moved to the new models folder. Expanded training logic to use a balanced sample (by right/left hand and gesture), extend training by a few epochs per prediction class.
• Model Classes: Added an "other_gesture" class and corresponding data intended to classify hands that aren't making any particular gesture, intended to map to no action. This non-gesture includes a larger dataset, and the model should always be trained with a larger sample of this, perhaps as large as all other samples combined (it's currently about 1/3 of the data sampled).
• Landmark Normalization: Unified normalization of hand landmarks using mean-centered normalization, dimension by dimension, with scaling based on maximum deviation from the mean in that dimension.
• CRUD: Added methods for CRUD (create/read/update/delete) functionality for gestures, contexts, and gesture-action mappings in crud.py in the src folder. Minimally tested but they all seem to work.
• Dev/Testing Notebook: Added a notebook for development/testing. Currently includes sample code for running data capture for new gestures as well as for training a new model after gestures are created, deleted, or altered. Intended for use in development/testing of CRUD functions as well as supporting functions so the UI can be developed separately.
• Streamlit UI for configs: Broke it; it's going to need to get expanded to handle the new range of CRUD functions.
• Archived python files, configs, data, and models not currently in use