Moved lib/msf/http/jboss/bean_shell_script.rb to
lib/msf/http/jboss/script.rb. Moved head_stager_jsp to script.rb.
Removed stager_jsp to use the function from the mixin.
The module allows to deploy a WAR (a webshell for instance) using the
BSHDeployer.
Also refactored modules/exploits/multi/http/jboss_bshdeployer.rb to
use the new Mixin (lib/msf/http/jboss).
The jboss_bsheployer as is does not allow to deploy a custom WAR file.
It is convenient when ports are blocked to be able to deploy a webshell
instead of just launching a payload. This will require a auxiliary
module which will use the JBoss mixin methods.