feature request - resolvers dns

[ozbillwang]

In version 1.6.x, new session resolvers was added to support DNS name service and dynamic IP backend.

https://cbonte.github.io/haproxy-dconv/configuration-1.6.html#5.3.2

So we need add it to templates as:

Example of a resolvers section (with default values):

   resolvers mydns
     nameserver dns1 10.0.0.1:53
     nameserver dns2 10.0.0.2:53
     resolve_retries       3
     timeout retry         1s
     hold valid           10s

raise this first, and will implement it soon.