Enable reflective method calls in Scala.

This adds an import to explicitly enable reflection-based calls on
structurally typed objects. Without this, it still works, but it raises
a warning. (In future versions of Scala, the import may be mandatory.)
Move to a properties file for configuration.

This makes the code more shareable (maybe eventually?) and also reduces
the amount of duplication between the Scala and Lua code.

There are some hoops I jumped through in the Scala to make it so that
the properties file was also an executable Lua script, mainly some
different handling of strings and cygwin paths. It's not too bad though,
and pretty well contained to a single method.