Add recipe to install Open JDK 8

I tested a few java builds and everything ran fine.

@BanzaiMan feel free to drop 9c466abb39ec8ae91a838454f7760c6ced5ea044 (additional jdk_switcher aliases)
Yep, I agree but `7` is not more confusing that `1.7.0`, `1.7`, `7.0`. The idea was just to extend this alias list, to provide the handiest ones.

As said above, there is no need for that addition. Just tell me if you prefer to remove it.