rename user moderator privilege
add "admin" privileges for the specific privlege groups

Also, reorder and reassign the integer values representing
the privileges.
shorten privilege mapping code

Instead of endless if/else or switch/case constructs,
use a static array to find privilege by name or name
for privilege.
Also, support the new privileges by simply including
them in the mapper array.
add a function to return the admin privilege for a privilege
add function to set user privileges
add API to give privileges to other users

Only the responsible admin can give a specific privilege
to a user.
change API and internal methods to allow privilege removal

Privilege removal requires the same privileges as
authorization.
remove old usages of 'admin' privilege

The old 'admin' privilege is now only used for giving
group admin privileges to others.
require registration-admin for registration of reserved user name
Merge pull request #34 from Library-Distribution/admin_privileges

Rework admin privileges