Allow crawlspaces/basements with only Walls

[shorowit]

Pull Request Description

Allow users to define above-grade crawlspaces/basements that only use Wall elements (i.e., no FoundationWall elements) for flexibility. Previously our Schematron rules would prevent it.

Checklist

PR Author: Check these when they're done. Not all may apply. strikethrough and check any that do not apply.

PR Reviewer: Verify each has been completed.

• Schematron validator (EPvalidator.xml) has been updated
• Sample files have been added/updated (openstudio tasks.rb update_hpxmls)
• Tests have been added/updated (e.g., HPXMLtoOpenStudio/tests/test*.rb and/or workflow/tests/test*.rb)
• Documentation has been updated
• Changelog has been updated
• openstudio tasks.rb update_measures has been run
• No unexpected changes to simulation results of sample files