Refactor TMFCore variables constructors

This pull request starts the work needed to pull TMFCore variables constructors values from properties in the classpath, rather than from strings.

More work is needed, but what we have here should be in the right direction to make the core more easily testable.

I needed to merge this with other conflicting changes I did. The bottom line is that I'm now using the definition of `unchecked` provided by @thermz rather than the `uncheckedVoid` provided by me.

No other functional change should be enailed by this pull request.

Lightly tested on both the `cli` and the `war` repos.