Fix for #105: Updated HadoopSecurityManager_H_2_0.java and ant build file

This PR includes the updated HadoopSecurityManager_H_2_0.java and moved a few classes in azkaban.security.commons to its own directory so they can be used in both hadoopsecuritymanager and hadoopsecuritymanager-yarn.
The point I was trying to make earlier is that all of these constant string definitions are unnecessary -- just reference the HiveConf ConfVar instead (preferably using a static import).