Adopt layout from https://github.com/fulldecent/swift5-module-template

[fulldecent]

(Posting issue to confirm it is in the project scope. I am planning to commit resources to work on this.)

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A modern project layout for Swift modules is defined at https://github.com/fulldecent/swift5-module-template

Work plan

• Study best practices at link above
• Apply the "Recipe" from the Swift 5 Module Template to this project
• Ensure that PR does not change the current development team

Follow-on work

• Make a minor version feature release with this updated project