Plugins to define tasks

[claudiu-cristea]

Right now the provided tasks are hardcoded in CollectionFactory. This limits a 3rd party to extend the system with new tasks. Move to a plugin system, where tasks are provided as plugins.

[geek-merlin]

I thought in the same direction too. But: Adding a plugin / discovery system for tasks will result in a lot of code complexity, and basically double command discovery.
We already have command discovery, and with #159 we can invoke them in runner.yml without the drabacks of a new command line process.

So proposing this is a WONTFIX.