Remove Java requirements for Debian/Ubuntu package
Remove Java requirements for Debian/Ubuntu package

Ref sbt/sbt#2931
Ref sbt/sbt#3105

Requiring `"openjdk-8-jdk"` prevents sbt 0.13.15 update on Ubuntu 14.04 LTS "Trusty Tahr."
Since there seems to be no reasonable way to depend on JDK 6, 7, or 8 without breaking some distro or use case, I'm going to remove the requirement here.

mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt-launcher-package,sbt/sbt,xuwei-k/xsbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,sbt/sbt-launcher-package,xuwei-k/xsbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt