Improve unreleased change report

Add a script to sort the version tags so that list_unreleased_changes.sh
does not pick up "eol" tags and other values that shouldn't be considered
when determining the most recent tag.

Start a script for printing standard format release notes for a
repository, given the version range. Use that script to expand the
information printed by list_unreleased_changes.sh.

Change-Id: Id091d697810ba7d65ae64fd2e52fd09cd78baf59
Merge "Improve unreleased change report"