Renames and moves file operator-editing-code.xml

I noticed that operator-editing-code.xml is not exactly valid as of now, since
the same steps are valid for developers and may be for architects in future.
This files is thus, moved to common folder and also renamed as editing-code.xml

Change-Id: I797f981a73e696d878c377f7ef9a69d1d2680dbd
Implements: blueprint separate-folders-for-books