Added class Jython.Jython_Launcher, for bundling Jython scripts in a jar for distribution

A class for running Jython scripts as ImageJ plugin. For single jython file it's easy to copy the file under plugins/scripts/, but for multiple files packaging them in a single jar file and hand it to user would be convenient. 

The code is from
<http://fiji.sc/Jython_Scripting#Using_a_jython_script_as_a_plugin>