Added support for compensation event definitions by using 'org/activiti/...

Added support for compensation event definitions in diagrams by using 'org/activiti/icons/compensate-throw.png' and 'org/activiti/icons/compensate.png'. After running 'ant clean distro', deployed activiti-explorer.war to Tomcat and upload a process definition that has both throw and catch compensation event definitions. You can check the result:
![](https://cloud.githubusercontent.com/assets/3234929/5021412/b3968f8e-6add-11e4-8f01-82655296f4ae.GIF).