Adds default to input_configfile param

[jlashner]

Adds default to input_configfile so it can be run from ocs-web

Description

Adds default to input_configfile so it can be run from ocs-web

Motivation and Context

so it can be run from ocs-web w/out providing a path

How Has This Been Tested?

not been tested yet

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[BrianJKoopman]

Just needs a docs update as well.