Add PDI Groovy Console plugin

Adds a Groovy Console to Spoon, which allows you to do Groovy scripting inside the Spoon IDE using the Kettle APIs.

Related blog posts:

http://funpdi.blogspot.com/2012/10/getting-groovy-with-pdi.html
http://funpdi.blogspot.com/2012/10/groovy-console-spoon-plugin-update.html
http://funpdi.blogspot.com/2012/12/groovyconsolespoonplugin-with-jsr-223.html