title: Nuget a plugin mvvmcross, interface not registered
body: <p>I've got a plugin for mvvmcross using nuget.</p>
  
  <p>When I try and use the plugin it tells me that an interface under the namespace of the plugin hasn't been registered.</p>
  
  <p>Is there anything else after adding the plugin to my project via nuget that I need to add into my solution?</p>