engine:

Fixed some logic in an assertion.
engine:

Updated parse_config to have less side-effects, and simplified its
return interface.

Instead of creating Input records, we just return a dict of the input
model file paths and leave the Input creation to a later function in
the workflow.
engine:

Updated hazard and risk calc creation functions to match the new
interface for parse_config.
tests:

Made all tests pass with the changes to engine.parse_config.