Added an LDAP/PowerDNS driver
Added an LDAP/PowerDNS driver

This driver is largely for internal WikiMedia use.  It will probably
need a fair bit of tinkering for any other deployment.

Related to blueprint public-and-private-dns.

Change-Id: I8636296192aecffedf363bd10a4ae761f7f6e6c3

n0ano/gantt,n0ano/gantt