🧹 Allow users to configure parameters in YAML rather than Python

[DavidOry]

Parameters are currently configured in a parameters Python script. This can be challenging for users less familiar with Python to work with, as specifying a Python path is more challenging than pointing to a YAML file. This has come up in WSP's deployment for the Utah DOT.

Anything to add @i-am-sijia?

[e-lo]

This capability already exists, but I'll submit a quick PR that better documents it. In fact, the only thing that python is doing is loading DEFAULT parameters...you shouldn't update any parameters in python at all.