Added support for forward zone type

Modified the zone erb template to have the correct behaviour when
zone_type = forward.

a simple example zone is:
dns::zone { 'example.net':
  zone_type => 'forward',
  forwarders => ['10.0.0.1','10.0.0.2']
}

there's more work that could be done to make the solution more elegant,
but at least it works. the db file is still created, even though it is
not used.
Restructing template to not contain blank lines.
Changing default values for SOA, causing syntax errors

since the template for the zonefile already appends a dot (.) there is no
need to add a dot by default to the values being passed into the template,
resulting in SOA.. and SOAEmail..