Trying out Jython 2.7.

This does a few things:

* No longer uses the Jython version that ships with the IDV.
* Doesn't extract the contents of the "jythonlib.jar".
* Updates the startup scripts, ant build, and install4j config to use the McIDAS-V Jython JARs.
* Fixes some deprecation warnings in `JythonManager`.
* (Appears to) fix the problem with using the `with statement`.