openssh-x11-jdk: replace openjdk with oracle-jdk

Strongly recommended by android-studio and now available with ubuntu as a base
image.

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
Merge pull request #23 from kemitix/feature/switch-to-oracle-java-7

openssh-x11-jdk: replace openjdk with oracle-jdk