3 - add missing functions (FIXED)
5 - review per-target error handling
7 - dn cache and cache exploitation to refine the candidate selection (?) (FIXED)
9 - review the group and attribute stuff (also in back-ldap!) (FIXED, need to
12 - rework compare and bind to attempt to operate on all candidate entries
13 while checking at most one succeedes
15 - clear previously bound targets when the bind is repeated