title: Can't deploy vaadin project
body: <p>i have a little vaadin project for a school project that originally deployed well and worked.
  i am using jboss as 7.1.1, vaadin7 and jdk8. My target platform is a raspberry pi running raspbian os.
  so i am using the pi4j library to access the gpio interface of the raspberry and everything worked just fine until i implemented a check for null when creating a new instance of the web page. at first the error was because somehow the "jboss/standalone/deployments/roboterarm.war/WEB-INF/..../classes" directory became empty. afterwards the error came to eclipse as i could not use the pi4j library anymore. i did not touch the libraries and i can't figure out why it suddenly stopped working. i reinstalled eclipse, jboss and redownloaded all the libraries but i still can not use anything, not even in normal java applications!
  afterwards i grabbed a copy from SVN that used to work normally but no luck there either, i can not use the pi4j jar-files.</p>
  
  <p><img src="https://i.stack.imgur.com/BjWsU.png" alt="my build path"></p>
  
  <p>everything looks fine to me there, yet it fails to give me code completion or compilation</p>
  
  <p><img src="https://i.stack.imgur.com/g7lie.png" alt="library does not get loaded"></p>
  
  <p>i also tried creating a new vaadin project and c&amp;p'ing the source code into the new project but the jar files are not recognized there either.</p>
  
  <p>What am i doing wrong? how can i fix this? thanks in advance!</p>