Adds Comments to magento2 recipe and modifies DocGen, to be able to e…

…xplain artifact deployment (#3510)

* adds sticky to writable recipe

chgrp for all files, chmod g+rwxs for directories, chmod g+rw for files

* adds artifact deployment for magento2 recipe

* Updates Documentation

* removes mode that has been submitted in other MR

* adds divers discussion results from PR #3317

- uses contrib/cachetool
- removes task build:prepare-env
- comments additional_shared_files and additonal_shared_dirs
- avoids invoke()

* updates docs

* corrects additional shared

* expands DocGen for artifact deployment and adds documentation to the magento2 recipe

* corrects missing capital and typo

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Co-authored-by: Anton Medvedev <anton@medv.io>