Created symlink for /var/lib/logstash/logstash.jar

The puppet manifests expect it here. If you'd prefer that, i could also change it in the puppet manifests.
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
Update mongodb.rb

Fix for LOGSTASH-1371
Merge pull request #658 from pieterlexis/debian_packaging

Improve Debian packages
Merge pull request #596 from hco/patch-1

Created symlink for /var/lib/logstash/logstash.jar
Merge pull request #659 from bitsofinfo/master

Update mongodb.rb w/ fix for LOGSTASH-1371