Feature Request: Custom Tasks

[vovimayhem]

I like the idea of how npm allows tasks to be defined in the package.json file.

Currently at IcaliaLabs, when we use plis inside a project, the most executed tasks are these:

• plis run postgres restoredb some_database_name path/to/some/database.dump (Uses a script restoredb to restore a database from a dump file)
• plis run web rails db:migrate searchkick:reindex:all another:rake:task (Runs a bunch of rake tasks in a rails project)
• plis build service_a service_b service_c (Re-builds the dockerfiles referenced by the compose project)

Maybe we should be able to define these tasks in a file similar to how npm's package.json does.

IMPORTANT Having a config file must not be mandatory.

Would this file be a json? a YML?