Bundle ingest-geoip and ingest-user-agent plugins
Bundle ingest-geoip and ingest-user-agent plugins

Filebeat modules require the ingest-geoip and ingest-user-agent
Elasticsearch modules.

Pre-bundle those modules to improve the out of the box experience with
Filebeat.

Also move the plugin list to a jinja2 variable at the top
of the template file to make it easier to adjust in the future.

Closes #48

jarpy/elasticsearch-docker,jarpy/elasticsearch-docker