Decide on "default" surge behavior

[hgp297]

Context:

• Surge factors are calculated based on user input PGA and user input PGA at DE
• These are currently specified as 1.0 and 1.0, respectively, in data/default_inputs.json, meaning the default behavior is to not trigger surge

Action:

• Determine if surge should be elevated to a required user input
• If elevated, move surge settings from data/default_inputs.json to examples/<model>/general_inputs.json, and correctly point downstream references
• Document or explicitly state the current no-surge default