Update ckeditor.d.ts getData and setData

FIXED getData() to allow calling without parameter as in the example

http://docs.ckeditor.com/#!/api/CKEDITOR.editor-method-getData

FIXED setData(...) parametes 

http://docs.ckeditor.com/#!/api/CKEDITOR.editor-method-setData
Merge pull request #2990 from damianog/patch-11

Update ckeditor.d.ts getData and setData