"monitoring packs" are simple tar.gz files that contain a file
`config.tpl` + additional supporting files. When a user indicates via
parameter that they want to use a monitoring pack, the bpm plugin goes
through these steps:

1. Unpacks the file into `~/.bpm/nodes/<node-id>/monitoring`
2. Appends the file `~/.bpm/nodes/<node-id>/monitoring/config.tpl` to
   the internal filebeat configuration template
3. Renders the combined template
4. Starts and stops the filebeat container togeth with the other
   containers when needed

This allows bpm to serve monitoring data and logs to all possible
filebeat outputs. Optionally the monitoring pack can contain additional
files like TLS certificates for authentication against monitoring
endpoints.

To separate the configuration of the environment (e.g. monitoring) and
the configuration of the actual node I've added a new lifecycle step:

- set-up-environment
- and for completeness sake (even if currently unused): tear-down-environment

The `set-up-environment` lifecycle step comes before `create-identity` and
`create-configurations` and is supposed to set up the runtime environment
for the node but not the node itself.