Common dependency package

Using cdd-dev introduces dependency from cdd-common 

Creates common registry for all CDDs in /etc/cdd
Configuration file /etc/cdd/cdd.conf
Set DBBACKEND (currently only unixgroups implemented)
Settings can be overridden by /etc/cdd/<cdd>/<cdd>.conf
cdd-role: add/remove roles in registered CDD
cdd-update-menus: add menu to all CDD users
(users have to call update-menus if not done in postinst script)
cdd-user: add/remove user to role of a registered CDD