Change license for adoc (guide) files to ASLv2

We plan to change the licensing of the adoc files from CC BY-SA 3.0 to ASLv2. Approval is sought from the following main contributors:

WAITING FOR APPROVAL
no more approval awaiting

APPROVED CHANGE
https://github.com/mojavelinux [Dan Allen]
http://hamletdarcy.blogspot.fr/ [Hamlet D'Arcy]
https://github.com/bura [Andrey Bloschetsov]
https://github.com/jeffbrown [Jeff Scott Brown]
http://twitter.com/CedricChampeau [Cédric Champeau]
https://github.com/ddimtirov [Dimitar Dimitrov]
http://twitter.com/werdnagreb [Andrew Eisenberg]
https://github.com/christoph-frick [Christoph Frick]
http://twitter.com/marioggar [Mario García]
http://twitter.com/paulk_asert [Paul King]
http://twitter.com/glaforge [Guillaume Laforge]
http://twitter.com/pledbrook [Peter Ledbrook]
https://github.com/dnahodil [David Nahodil]
https://github.com/jnorthr [James Northrop]
https://github.com/marcpa00 [Marc Paquette]
https://github.com/PascalSchumacher [Pascal Schumacher]
https://github.com/stavytskyi [Maksym Stavytskyi]
https://twitter.com/asteingr [André Steingreß]
https://github.com/EPadronU [Edinson Padrón Urdaneta]
https://github.com/keeganwitt [Keegan Witt]
https://github.com/tobia [Tobia Conforto]
https://github.com/michaelss [Michael Schuenck]
https://github.com/davidmichaelkarr [David Michael Karr]
https://github.com/grantmcconnaughey [Grant McConnaughey]

Note, this list has been created from the contributors.adoc file within the Groovy codebase. It is meant to be kept up to date with the main contributors. If someone submits a very small typo, they might not get added - however, anyone who has contributed even a small typo is welcome to comment here. And if anyone has accidentally been left off this list, please let us know.