drop debian/

debian packaging will be on separate branch now
update pgsql plugin documentation

+ add SSL verification options
+ replace PGCLUSTER with PGHOST, former cements the use of a specific
  version of postgresql-client.

Git-Dch: Full
prefer local plugins over ones from a distro package
bash style fixups

* [[ for less quoting
* -eq instead of = for numerical equality
* text manipulation instead of forking a basename(1)
implement hostname filtering

Fixes GH-1.
implement caching for filtered version

filtering can take a long time, about 1m for 20k key entries