Allow built in Commands to be disabled by the user

[ntindle]

All users must include the list of built-in commands in their prompts. This causes poor user experience, such as that listed in #3428.

We should support disabling command categories by the user.

Proposed Solution: add another config that disables loading a command if the configuration is in the list of disabled commands

Tasks:

• [ ] #3663 Move all command registrations into main.py
• [ ] #3667 Add an env.template entry for DISABLED_COMMAND_CATEGORIES and use it in main.py
• [ ] #3669 Document the available categories

[Emasoft]

Commands should be removed and converted in plugins.

[ntindle]

@Emasoft see #3652