title: Android: how to share code between projects signed with the same certificate
body: <p>In Android <a href="http://developer.android.com/intl/de/guide/publishing/app-signing.html" rel="noreferrer">documentation</a> concerning code signing we can read: "<em>By signing multiple applications with the same certificate and using signature-based permissions checks, your applications can <strong>share code</strong> and data in a secure manner.</em>"</p>
  
  <p>How exactly such code sharing can be done? Is it possible to release main application and multiple exchangeable plugins then discover them at runtime? What does source code looks like and what are advantages over "standard" intents calls from/to different APK packages?</p>