#2 Create Components in codebehind

[Nick Stolwijk]

Controller needs a method, through which Codebehind,
Actions and maybe others can request a new instance of
the various implementations used. I.e. if an Action
needs a FileDialog, it can ask the Controller
.getImpl("FileDialog"). The Controller will return a
new instance of FileDialogImpl which is specified in
the guiml.config file. To let this work, Actions also
needs a reference to the controller, through the
execute(Controller c) method instead of an execute()
method.