Add java 7 support & modify extract behavior to work across java upgrades

This recipe originally exited if java7 was being used, I removed that - it wasn't necessary. The other problem with the pattern of only extracting the JCE zip when it is downloaded is that when java is upgraded, JCE doesn't get re-extracted into the new java directory. I modified the recipe to check for the existence of the .bak files this recipe creates and if they aren't present it'll re-extract the zip to java_home. It feels like there should be a more elegant solution - but I couldn't come up with one in the time I had. 

It seems like ideally this whole recipe would be part of the normal java cookbook so that java version changes can more easily trigger a re-extract.