Refactor the code for hypotetical events

[micheles]

Written by @nastasi-oq and @CB-quakemodel for PAPERS, living in the secret branch papers-phase3 as module.py

[micheles]

After review, let's keep it as it is for the moment.

[micheles]

We should at least decouple Django from the scientific logic and add a Django-independent command-line test, otherwise the code cannot be debugged without an indecent effort.