Add notebook-remove command line option

[aiguofer]

All the code for removing notebooks was there, not sure why the command line option was never actually added.

[jeffkowalski]

I think the code was present, but commented-out because it was thought to be too dangerous. Deleting a note at once was OK, but deleting whole notebooks or tags without the ability to undo could cause real stress, and was left to the heavier apps.
Nonetheless, I'll consider merging this code back in.
Caveat emptor ;)

[aiguofer]

Yeah that makes sense. I think with the built in confirmation this should be a non-issue. I could add something to the prompt indicating that this can't be undone if that would make it more 'user friendly'.