NEW PROVIDER: NETCUP (DNS) (#718)

* Add support for netcup DNS api.
* Add documentation page.
* Update reference to new version path.
* Add OWNERS entry for netcup.
* Add credentials for integration test. Netcup does not support PTRs. Fix parsing/formating of SRV records.
* Skip integration tests that are not supported.
* Use single quotes in JS code.

docs/_providers/netcup.md

@@ -0,0 +1,38 @@
+---
+name: Netcup
+title: Netcup Provider
+layout: default
+jsId: Netcup
+---
+# Netcup Provider
+
+## Configuration
+In your credentials file, you must provide your [api key, password and your customer number](https://www.netcup-wiki.de/wiki/CCP_API#Authentifizierung).
+
+{% highlight json %}
+{
+  "netcup": {
+    "api-key": "abc12345",
+    "api-password": "abc12345",
+    "customer-number": "123456"
+  }
+}
+{% endhighlight %}
+
+## Usage
+Example Javascript:
+
+{% highlight js %}
+var REG_NONE = NewRegistrar('none', 'NONE')
+var NETCUP = NewDnsProvider('netcup' 'NETCUP');
+
+D('example.tld', REG_NONE, DnsProvider(NETCUP),
+    A('test','1.2.3.4')
+);
+{%endhighlight%}
+
+
+## Caveats
+Netcup does not allow any TTLs to be set for individual records. Thus in
+the diff/preview it will always show a TTL of 0. `NS` records are also
+not currently supported.