Renamed NewMailSheet to NewMailWindow

Also converted from sheet to window
Shows select box with accounts in new mail editor

To accomplish this, a new facade was introduced. Also, there is now a
base facade which encapsulates the object context params foo.
Bound selected item for account selector
Body text field accepts return
Constantly update bindings
added additional labels
Can create new mail from menu item

Apple says, that every toolbar item should also be available as an menu
item. Toolbar items are only for quick access.

http://stackoverflow.com/a/1249309/2381404
removed unused menu items below File