Add DESCRIPTION and RT VERSION sections

Add DESCRIPTION to encourage adding some detail to explain to users
why they would want to install the extension. Can include usage
details, screenshots, etc.

Add RT VERSION to explicitly note what versions of RT the
extension is known to run on.
New Plugin() vs @Plugins
Merge branch 'add-description-and-version'
bump copyright
update build infrastructure
Call out useful things to set in your Makefile.PL
tidy and update Changes
update for 0.08