Openjdk8 cartridge

Hi,

Here is a pull-request for adding an OpenJDK 8 add-on cartridge (commit e85559d) with added support for it in the jbossews cartridge (commit ade7a7a). Right now the env variable is arch dependent. Since the java-1.8.0-openjdk package installs into /usr/lib/jvm/java-1.8.0-openjdk.x86_64 for x86_64 and /usr/lib/jvm/java-1.8.0-openjdk for i686. I'm not sure which arches are supported so I went with this for the time being. Please let me know if this needs changing. If so I'd appreciate pointers on how to solve this using a Ruby snippet :)

Let me know what you think!