Rewrite node operations to use bash scripts to start, stop and backup the node

[sduchesneau]

Remove the heavy logic (in this repo and injected from firehose-*** repos) for snapshots, node operation, etc. bash scripts should be provided by the user (copied from examples with sane values).

• start : starts the node and outputs the logs to STDOUT and STDERR as usual
• stop: stops the node
• backup: runs the backup, it can call curl localhost:8080/v1/stop|start if needed
• restore: runs the backup, it can call curl localhost:8080/v1/stop|start if needed
• heartbeat: this script is run in a loop, sleeps 1sec between runs. (optional, new feature request: * onfailure: this script is run when the node suddenly stops. It can decide to call 'restore' or 'shutdown' or just 'start' or whatever logic)

the node manager API listens on 8080:

• start, stop, shutdown, backup, restore

strong suggestion: We get rid of the "node" type of service, only reader remains

[maoueh]

Every being standard "execution, it's easy to use bash script to control "node" software:

reader-node-binary: bash
reader-node-arguments:
- -c
- ...

There is a also reader-node-bootstrap-data-url that accepts bash://<absolute-path-to-script> so just bootstrapping from bash is also possible.