Update WindowManager to include parameter getter/setter as in 3.x

This adds getter/setter methods for additional window parameters. In addition the parameters can be set when opening/creating a window, as in TinyMCE 3.x, eg:

editor.windowManager.open{..., {"key" : value}}
Merge pull request #197 from ryandemmer/patch-1

Update WindowManager to include parameter getter/setter as in 3.x