Active Directory support

[coudot]

For a lot of features we need to write specific code for Active Directory support (password change, locking, ...)

We have some issues linked with this:

• How to honor password history restriction (Active Directory + password change as manager) self-service-password#927
• LTB Service Desk Active Directory Support service-desk#52

My idea is to create an Interface and have implementations for standard LDAP and Active Directory.