Please add these license files to the jars to make them redistributable

These files will appear in the root of the generated jar files, which is
essential to make the binary jar file redistributable.  (The -with-dependencies jar file would need additional information in LICENSE.txt about Rhino, and a LICENSE-Rhino.txt file.  I could not easily figure out how to make the two artifacts differ, so I deferred that task.)

Without these files, most legal departments will recommend against redistributing the jar files, which complicates greatly selling a third-party solution that integrates with Force.com.  With these files, the jar files become redistributable, making integrations easier to package, sell and install.

I'm not terribly proficient with Maven, so if there is a better way to add files to these jar files, please let me know and I'll take a stab at it.

Thanks in advance for taking the time to review this proposed change.

-aB