official/delete_long_tags : add a usage section
official/save_selection : new script

This scrips adds a shortcut to manipulate multiple selection save-buffers
Improve readme, add a note about headers
official/generate_image_text : rework header
official/hello_world : document and reindent
include_all : new script

This will look at all scripts and create configuration options to easily
enable/disable the scripts from within darktable
official/generate_image_txt : use coroutine.yield  now that it's fixed