Fixed NuGet.config for access to prereleases.

Author: AndyButland

NuGet.config

@@ -1,22 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
   <packageSources>
-    <clear />
     <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
     <add key="Umbraco Prereleases" value="https://www.myget.org/F/umbracoprereleases/api/v3/index.json" />
     <add key="Umbraco Nightly" value="https://www.myget.org/F/umbraconightly/api/v3/index.json" />
   </packageSources>
-  <packageSourceMapping>
-    <packageSource key="nuget.org">
-      <package pattern="*" />
-    </packageSource>
-    <packageSource key="Umbraco Prereleases">
-      <package pattern="Umbraco.Cms.*" />
-      <package pattern="Umbraco.Deploy.*" />
-    </packageSource>
-    <packageSource key="Umbraco Nightly">
-      <package pattern="Umbraco.Cms.*" />
-      <package pattern="Umbraco.Deploy.*" />
-    </packageSource>
-  </packageSourceMapping>
 </configuration>