Interactive prompts

[multimeric]

At various points it makes sense to ask the user between a small number of options. We can do this using menu().

For example, if they module_load("python") it probably makes sense to ask them which version they want.

If they module_load("X") and there is a dependency collision, we might ask them which option they want: to swap the colliding module with the new module, to cancel, or to purge and then load the new module.