I'ved changed/added the following; (please excuse anything wrong/not right, this is my first ever pull request)

1. Validate for the zone db files
2. Cleaned up tasks.yml;
    a. made some tasks multi-line to fit better on standard terminals
    b. changed an action: to template:
    c. added ability to sync include files
    d. The above would have --chown: {{ bind_user }}:{{ bind_group }} but this needs rsync 3.1 so only recent ubuntu/Debian compat
       so added workaround chown task
3. Added default DNS forwarders to Google DNS (so it works out the box if you don't specify one)
4. Added recursion option so bind can function as a cache server