Disable launcher and new directory in the root directory

[ellisonbg]

The root directory of the jupyter drives is not really a directory, but instead is a list of the buckets. Because of this, creating a file or directory is invalid. When a user tries to do this, in the current version, those operations fail. Right now the error messages are pretty cryptic. At a minimum, we should provide more informative error messages, but ideally, it would be nice to disable the UI in lab for creating files and directories when a user is in the top level of the jupyter drives. This may be a bit subtle though as there are so many paths for creating files, but we may be able to do this by disabling the underlying command. This may require changes to JupyterLab itself, so let's discuss.

[gogakoreli]

On the root level should we allow to create a bucket instead of the new folder? It will be more like a feature request and we won't need to disable the functionality any longer. Not sure how complicated that would be technically speaking since I can tell there is a reason we have a dedicated create a new bucket functionality.

[DenisaCG]

Thanks for opening this issue!

I merged this PR #85 which disables the commands which cannot be performed at root level (New Directory, New File, New Notebook, Upload and Launcher). The New Drive command is indeed a separate one that is now only enabled at root level, since #84. Both PRs address the toolbar functionalities, as well as the context menu ones.

As this is resolved, I will close the issue, but please feel free to follow up on it if it requires further discussion.