Upgrade to tomcat 7.0.50 and to support ELInterpreter in JSPC

1. Upgrade to latest tomcat version 7.0.50.  It removed xml validation feature. So there is a little bit code change for it.
2. ELInterpreter is interface to customize own java code for EL. It was supported after version 7.0.40. 
    We need this feature in JSPC as well.