Add a number of extension: OS-specific package names, ldap, AD-Auth

These are changes where made by hdeadman, and I would like you to add them, so I can continue to improve on them while minimizing drift between your repo, mine and his.

They add 
- ldap based authentication, incl. AD support
- set the package names based on the os-family.

They are currently lacking seperate test, but that is one thing I will work on.

hdeadman did not want to work through a pull request, as the changes are sufficient for his purposes.