Remove triple slash directive in favor of modern `import` syntax

[tommagnusson]

This would include removing the outdated namespace keyword.

• https://www.typescriptlang.org/docs/handbook/namespaces.html
• https://stackoverflow.com/questions/32805559/typescript-es6-import-module-file-is-not-a-module-error
• https://stackoverflow.com/questions/30357634/how-do-i-use-namespaces-with-typescript-external-modules

@labouseur

[tommagnusson]

Benefits:

• Modularize code
• Explicitly denote an entry point
• Force explicit dependency declarations (host should never depend on os)
• Ability for unit testing with frameworks like Jest (running on Node environment would be no issue)

Drawbacks:

• considerable refactoring process
• Possible drain brammage