Add Oracle JDK 1.7 recipe for Linux and OS X

This recipe is a little weird because it has to do the actual downloading of Java from within the build script because Oracle requires you to accept a license agreement (which sets a cookie) in order to download it. I've made it so that the `pre-link.sh` script asks you to confirm that you accept the license before you actually install things, so as not to anger the licensing gods.

There's no `bld.bat`, so this doesn't work for Windows.