Add recipe to install Open JDK 8

:construction: **work in progress, please don't merge yet** :construction: 

I tested a few java builds and everything ran fine, but there are still some open issues to address:

 * [ ] JFX (`$JAVA_HOME/jre/lib/ext/jfxrt.jar`, ...) is not packaged by `ppa:openjdk/ppa` (unlike `oraclejdk8` package from ppa:webupd8team/java
 * [ ] Is there other core components of JDK8 specification that are missing? (Nashorn is available, but I don't know yet a way to verify, excepted `diff -r`)
 * [ ] verify situation of Java Cryptography Extension (JCE) Unlimited Strength 

@BanzaiMan feel free to drop 9c466abb39ec8ae91a838454f7760c6ced5ea044 (additional jdk_switcher aliases)
I tend to think those are mistakes, too, but they're there already, and removing it may break stuff. I'm OK with leaving those, but against adding new ones.