issue #61: add applyttl to rrset by name and type command to cli

for issue #55

This allows the cli to apply a uniform ttl to a record set by name and type.  no output is returned if that set doesn't exist.

Example (note last arg is the ttl)
```
$ denominator -p mock record -z denominator.io. applyttl -n www1.denominator.io. -t A 10000
;; in zone denominator.io. applying ttl 10000 to rrset www1.denominator.io. A
;; ok
```