Support scriptText api to execute groovy scripts on the server
Jenkins features a nice script console[1] which allows users
to remotely run arbitrary groovy scripts on the Jenkins master.
Examples:
$ curl -d 'script=println("hello world")' -X POST
http://localhost:8080/scriptText
hello world
$ curl -d 'script=println(Jenkins.instance.pluginManager.plugins)' -X POST
http://localhost:8080/scriptText
[Plugin:windows-slaves, Plugin:ssh-slaves, Plugin:translation, Plugin:cvs,
Plugin:nodelabelparameter, Plugin:external-monitor-job, Plugin:subversion,
Plugin:ssh-credentials, Plugin:token-macro, Plugin:ant, Plugin:ldap,
Plugin:credentials, Plugin:matrix-auth, Plugin:matrix-project, Plugin:mailer,
Plugin:jquery, Plugin:maven-plugin, Plugin:pam-auth]
[1] https://wiki.jenkins-ci.org/display/JENKINS/Jenkins+Script+Console
Change-Id: Ia4fbfca970165d890d7e076f47ddcde7633afa9b
6e3daab97d