Fixed up the ClassPathViewer to use trees (i.e. JTree) for the
elements within a directory/jar file.
To see this,
Added the resolve() method to ExpressionInt for rewriting
the terms to be more efficient by looking up classes, etc.
Need to implement this in all the different expression types.
Added a GUI for interrupting the current Omegahat task.
Works for Java methods as well as Omegahat expressions,
but cannot cause a termination of a native method
until it returns control the JVM.
This will be integrated into a command palette to control
many other things.