Content pack support for parameter feature in Alerting

## What?
In 3.2 the alerting filtering now supports parameters and lookuptable parameters.
When exporting a event definition to a content pack the parameters need also
to be exported together with the lookup tables they referring.

## Why?
Users want to be able to export there whole configuration to share them with other users
or to use them as provisioning when re-creating there graylog instances.

## Your Environment
* Graylog Version: pre 3.2