Create "user" configuration files under pdns.d directory

[aromeyer]

As the defaut configuration of powerdns is only a documentation of available parameters and their default values, modify the configuration tasks in order to leave default config untouched and to create user configuration file under the pdns.d/ directory

[aromeyer]

Sorry I am just strting to play with Ansible. I have tried to include in my last commit all your remarks but I was not really able to execute the tests. Nevertheless I have added to the test files what seems to me relevant for mysql and sqlite. Many thanks for your comments.

[aromeyer]

All comments have been normally included.

[pieterlexis]

Thank you, I am trying to test these changes but testing is harder than expected (this might require some more changes). I'll merge this once I get that right :).