Bug 17459: Add a script to create a superlibrarian user

Bug 17459: Add a script to create a superlibrarian user

This is for developers: it's quite long (many clics) to create a new
superlibrarian user.
This new script creates a new user with superlibrarian permissions with
the easy to remember credential koha/koha

Test plan:
  perl misc/devel/create_superlibrarian.pl
Log in to Koha using koha/koha

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>