Add the ability to specify resources from the unpacked JAR

[xkrogen]

The Dynamometer job makes use of resources which are within its JAR such as the start_component.sh script. If the JAR is first unpacked and individual files are added to the classpath, as with the hadoop jar command, this currently works fine. However it does not work properly if the JAR is not unpacked, since the file does not actually exist anywhere (it is within an archive). We should support this to properly run from a normal JAR.