Bug 17267 - Document koha-create --adminuser

Bug 17267 - Document koha-create --adminuser

A description of --adminuser was missing from debian/docs/koha-create.xml
This patch adds a description in the Options section, as well as under
DEFAULTSQL in the list of configuration variables.

To test:
Run these commands and look at the formatted man page:
$ xsltproc /usr/share/xml/docbook/stylesheet/docbook-xsl/manpages/docbook.xsl \
  debian/docs/koha-create.xml
$ man -l koha-create.8

Make sure this test passes:
$ prove -v xt/verify-debian-docbook.t

Signed-off-by: Liz Rea <liz@catalyst.net.nz>
Edited commit message to fix typo - koha-mysql -> koha-create as that's what we're testing. :)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>