Contextmenu plugin ctrl key and meta mac key configuration enhancment

CKEditor already supports showing the native browser context menu if the ctrl key is pressed (or meta mac key).  I actually needed the opposite behavior.  A client wants the default context menu to the be native one, and the ckeditor context menu to show when holding ctrl (or meta mac key).  I changed the way you would configure this in the editorConfig by using to config options, defaultContextMenu and ctrlContextMenu.