pkg/debian: compare strings correctly
pkg/debian: Implement better conffile detection
pkg/debian: Make the package better

 * Append date, time and git commithash to the local revision for non-releases
 * Add a url and short description to the package
 * Depend on 'default-jre' instead of a specific java version
Merge pull request #658 from pieterlexis/debian_packaging

Improve Debian packages
Merge git://github.com/logstash/logstash