CLI: allow `add` & `remove` commands to register & deregister mcps

mcpjungle add should be the same as mcpjungle register Same thing for remove

But these should not be added as separate commands, this will clutter the cli help message

Instead, these should become the main commands and the original ones should become their aliases

So:

register will be an alias to add deregister will be an alias to remove

This way, the help message starts displaying add and remove as main commands. But if a user invoked register or deregister, it still works for backward compatibility.