Extend METADATA scopes to include "file" scope

[tsandall]

Currently we have subpackages, package, document, and rule scoped annotations. These each of their own valid use cases however none of them are ideal for applying annotations to all nodes in the current file. The package scope can work however if multiple files contribute to the same package then we generate an error. It would be useful to have a file scope. The file scope annotation should precede the package directive (however the 'package' scope directive should still be the default.)