Support nested groups

[adoom42]

Please add support for nested groups.

Example:

• Add a directory from the Crowd web interface. Enable the 'Use Nested Groups' option.
• From the Crowd web interface, create a new group within the directory. You have the ability to add both users and groups as members. The Nested Members tab shows all users - those directly assigned as well as those who are members of an assigned group.
• Retrieve group information through crowd-ldap-server using a standard LDAP query. The 'member' attribute contains direct members, not nested ones.

[dwimberger]

Added support within the AD emulation. See Configuration for instructions on how to enable this new feature.