Add Modify-Increment Modification Support

[mp911de]

We received a ticket for Spring Data LDAP (DATALDAP-72) requesting support for Modify-Increment Modification. I think Spring LDAP is the appropriate place for this to happen.

Original description:

It would be nice if Spring Data LDAP allowed you to create modify requests with the type of Modify- Increment to meet this http://ldapwiki.com/wiki/LDAP%20ModifyRequest%20Operations.