Change StaticOptimizer's `DumpFolder` mechanism to something more elegant

[Lionel Parreaux]

Currently in order to dump the code generated by optimizeAs('Name), one has to write:

implicit val `/tmp` = DumpFolder

It would be less cryptic and more general to implement a static macro so we can do:

implicit val dumpFolder = static{DumpFolderPath("/tmp")}

Can use annotations to store the intermediate AST. Can even execute the code at compile-time and use a type-class to parse the result back to an AST.