indexers implementation is now separated from settings/definition

so we can have multiple newznab definitions.

NzbDrone.Core/Indexers/Newznab/NewznabSettings.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace NzbDrone.Core.Indexers.Newznab
+{
+    public class NewznabSettings : IIndexerSetting
+    {
+        public String Url { get; set; }
+        public String ApiKey { get; set; }
+
+        public bool IsValid
+        {
+            get
+            {
+                return !string.IsNullOrWhiteSpace(Url);
+            }
+        }
+    }
+}