dry and go direct to .deb

The wolfnet PPA has become obsolete.
Fortunately, the logstash project is now building their own .debs.
Pull that directly for install.

Also, DRY out a few strings to variables.
Revert "move processing from shipper to indexer where it belongs."

This reverts commit 20d698cd4690b87ff34a231917015a983b3593e0.

After talking with folks in the logstash channel, I think the
very minimal processing we have so far _needs_ to be on the
shipper.

More intensive processing should be put on the indexers though.