add, call modules by Emacs key bindings

[nbehrnd]

Independent of recurrent runs of Memacs' modules by a service like cron, the manual launch from an instance of Emacs via Emacs' key bindings may be equally useful to other users. This approach is documented on the example processing photos.

[nbehrnd]

With Mickey Petersen's tutorial-like presentation of Emacs' key bindings in hand, it became easier to define such. The example equally is a showcase of what I aimed for (noted in an earlier issue report here).

[novoid]

Oh, thanks for that input!