Geoserver seeder

Complete ruby script to seed a geoserver based on metadata records.

Seeding all layers in metadata, zoom levels 2-6, 8 concurrent threads:
```
./geoserver_seeder.rb -u http://catalogue-123.aodn.org.au/geonetwork -g http://geoserver-123.aodn.org.au/geoserver/wms -s 2 -e 6 -t 8
```