Editors: Automatically add editor/document id to context and use that

instead of manually adding a context everywhere.

Change-Id: I4336015a6d19349171a255e949da89b0013d6700
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/pythoneditor/pythoneditor.cpp

@@ -62,7 +62,6 @@ class PythonEditor : public BaseTextEditor
 public:
     PythonEditor()
     {
-        addContext(Constants::C_PYTHONEDITOR_ID);
         setDuplicateSupported(true);
     }