Organize package scripts in submodules

[aspeake]

Separate the common user scripts (ecm_prep.py and run.py) and the input generation modules into separate submodules. /supporting_data and constants.py are likely the only shared resources for the two.

We may potentially want to introduce entry point(s) to more easily run the user scripts too. Being able to run, for example, scout run --args or scout ecm_prep --args is easier than traversing several directories.