Fixes for java-8-oracle

* Move headless JRE tools to separate headless section to match Ubuntu-provided jinfo for OpenJDK
* Add jcmd, jmc, and jvisualvm
* Sort items alphabetically in each section
Add jcmd, jmc, and jvisualvm to register_jdk8_for_update_alternatives.sh
Merge pull request #1 from InfernoZeus/java-8-oracle-fixes

A couple of fixes for Oracle's JDK8