Always use a YAML parser to read YAML files

[nrferguson]

batch_file.yaml is often read by parsing a specific line. This means that, when a line is added or removed, every script that reads the file needs to be updated, too.

List of scripts that read batch_file.yaml this way:

• build_scenario_networks.bat
• Submit_Full_Regional_Model_SOLA.bat
• trip_gen.bat
• create_transit_demand.bat
• run_transit_assignment.bat

Using a YAML parser will allow the file to be read without depending on line position. This may be a good reason to start to translating these batch scripts to Python.