Update selection tutorial part 1

[juanotto]

Several improvements:

• Updated all the images with screenshots using NB 27 on Ubuntu.
• Old images removed (they were only used here).
• Format using asciidoc to keep elements inside list items for steps with instructions.
• Text simplification, kept the general structure but modified the text quite a bit.

[juanotto]

@mbien @ebarboni have a look when you can. I applied the same types of changes as in the previous docs PR, but a lot more editing on the text for this one.

[mbien]

Text simplification, kept the general structure but modified the text quite a bit.

i like the streamlining! Reads good IMO.

left a few suggestions inline.

[mbien]

reads good now I think

[mbien]

if you think this is done, feel free to squash so that we can get this update in too