java 6 hasn't worked for a while now; deleting

I'm not sure why nobody noticed, but a number of classes in the framework no longer compile on Java 6 (mostly because of the try(Object foo = bar()) {} syntax). So I am removing the build path for Java 6 since it's been broken for a while now. Apparently once upon a time we had users who couldn't upgrade to Java 7 but that is apparently no longer the case, or we'd have heard about it by now.