Making main flow importable

[dericke]

I'm thinking of making a PR to separate the main function into one function for parsing CLI args, and then a main flow function that takes those CLI args as function argument(s). The aim here would be to make that main flow function easily importable to other scripts. I have one such script for PyQGIS that currently calls ogr2osm as a subprocess, and would like to instead import it as a module.

Would such a PR be welcome? It isn't guaranteed that I'll have the time to write this, but I'd like to look into it.