Move subpackages under nds

[charlesbmi]

https://github.com/agencyenterprise/neural-data-simulator/issues/40

Introduction

From user feedback:

Installing nds (with extras?) installs a package named decoder which is really generic and is overshadowing my local decoder.py causing problems for VSCode intellisense. Can this be renamed to nds_decoder or better yet, pull decoders into the nds pkg.

Changes

• Move core NDS functionality (encoder and Input/Output communications stack) into neural_data_simulator.core. This has some similarity to how pandas organizes code: https://github.com/pandas-dev/pandas/tree/main/pandas/core
• Move "extension packages" (decoder, streamer, recorder, tasks, plugins) under neural_data_simulator namespace, e.g. neural_data_simulator.decoder
• Lots of renaming in import statements to match the new code organization.

Behavior

• Code should work the same after running nds_post_install_config --overwrite-existing-files. (The import naming in the plugins has changed).
• Tested with unit tests and by running run_closed_loop locally

[charlesbmi]

Thanks Newton!