doc: Import Jeff Darcy's translator tutorial

It's way better than what we have currently. It's the original text from Jeff's
blog [1][2][3][4], unedited aside from the title, so that the content can be
properly attributed.

[1] http://hekafs.org/index.php/2011/11/translator-101-class-1-setting-the-stage/
[2] http://hekafs.org/index.php/2011/11/translator-101-lesson-2-init-fini-and-private-context/
[3] http://hekafs.org/index.php/2011/11/translator-101-lesson-3-this-time-for-real/
[4] http://hekafs.org/index.php/2011/11/translator-101-lesson-4-debugging-a-translator/

Original-Author: Jeff Darcy <jdarcy@redhat.com>

Necessary editing will follow:
* Nicer endings/openings of the subsections, as they are no longer separate articles
* Wrap lines in terminal outputs so that they render nicely in PDF
* Remove HeksFS references
* Remove first person fear of developer wrath for manual creation of a volfile

Change-Id: Ie9bb537b5817e8fa575ec0c66a58c48e6584698e
Signed-off-by: Lubomir Rintel <lubo.rintel@gooddata.com>
Reviewed-on: http://review.gluster.org/5480
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>