MAGMA-254: Migrate Js Engine from Rhino to Nashorn

[ymarcon]

Jira issue originally created by user @ymarcon:

And therefore improve performance. Java8 will be a requirement.

https://wiki.openjdk.java.net/display/Nashorn/RhinoMigrationGuide
http://stackoverflow.com/questions/22502630/switching-from-rhino-to-nashorn

[ymarcon]

Comment created by aprudencio:

the goal of this migration was to improve performance of JavascrioptDatasource using nashorn. However results have shown that there were not performance improvements due to implementation limitations of the nashorn engine (clearing the global scope requires parsing the script again).

since the goal was not met, this feature is kept on a separate branch.