coffee generate events to better track the external cycle of the commands

[vincenzopalazzo]

There are cases when during a command execution, it is nice to receive events back.

An example, during the install plugin, we should run

1. Install the pluigin
2. While installing, we want to know what the step coffee is running (searching the plugin, or build the plugin ecc)
3. report it to the user

In this was we can generate core lightning notification too at some point by listening to new events