Couple of API changes

[migueldeicaza]

Two important changes in the API.

1. Dictionary became GDictionary, to avoid clashing with Swift's Dictionary and having to prefix the Swift or Godot one every time you used one (I already had remapped String/Array to GString/GArray)
2. Methods that had redundant first argument name, drop the requirement for it. So setFoo (foo: Int, and: String) becomes: setFoo (_ foo: Int, and: String), so it your source code should look less cumbersome.