New DNS provider PowerDNS (#748)

* Added PowerDNS as dns provider

* Remove unnecessary comments

* Some tests

* Implemented feedback

docs/_providers/powerdns.md

@@ -0,0 +1,57 @@
+---
+name: PowerDNS
+title: PowerDNS Provider
+layout: default
+jsId: POWERDNS
+---
+# PowerDNS Provider
+
+## Configuration
+In your credentials file, you must provide your [API URL, API Key and Server ID](https://doc.powerdns.com/authoritative/http-api/index.html). 
+
+In most cases the Server id is `localhost`
+
+{% highlight json %}
+{
+  "powerdns": {
+    "apiurl": "http://localhost",
+    "apikey": "your-key",
+    "servername": "localhost"
+  }
+}
+{% endhighlight %}
+
+## Metadata
+Following metadata are available:
+
+{% highlight js %}
+{
+    'default_ns': [
+        'a.example.com.',
+        'b.example.com.'
+    ],
+    'dnssec_on_create': false
+}
+{% endhighlight %}
+
+- `default_ns` sets the nameserver which are used
+- `dnssec_on_create` specifies if DNSSEC should be enabled when creating zones
+
+## Usage
+Example Javascript:
+
+{% highlight js %}
+var REG_NONE = NewRegistrar('none', 'NONE')
+var POWERDNS = NewDnsProvider("powerdns", "POWERDNS");
+
+D("example.tld", REG_NONE, DnsProvider(POWERDNS),
+    A("test","1.2.3.4")
+);
+{%endhighlight%}
+
+## Activation
+See the [PowerDNS documentation](https://doc.powerdns.com/authoritative/http-api/index.html) how the API can be enabled.
+
+## Caveats
+Currently it is only possible to enable DNSSec while creating a new zone.
+On-demand activation/deactivation of DNSSec will be added later.