OpenJDK 6

Previously, a user could not successfully use OpenJDK6 with the
buildpack.  This change adds support for this type of JRE by adding a
download URL (based on an Ubunutu DEB package) and the knowledge of
how to extract the files from the download.

[#49321993]
Merge 49321993-open-jdk-6 to master

[Completes #49321993]