Adding Java convenience methods for adding GET handlers to a chain

Is this the kind of thing you want for issue #81?

I've just done Get at the moment.  Added it to the Java <code>DefaultChain</code> implementation and created a new spec specifically for testing the Java methods.

If this is right then you can pull this request and I'll send others as I'm doing the other methods.  Or just wait until I've done them all, whatever suits.