WIP: Feature/relax on pm list

The pm-list command has value in `any` drupal related context. This PR tries to relax on the bootstrap level and is intended for Drupal 8 only.

Feedback and hints are welcome.

```bash
cd /tmp
drush dl devel-8.x
drush pm-list

 Package      Name                                   Type    Status    Version
 Development  Devel (devel)                          Module  Disabled  8.x-1.x-dev
 Development  Devel generate (devel_generate)        Module  Disabled  8.x-1.x-dev
 Development  Devel Kint (kint)                      Module  Disabled  8.x-1.x-dev
 Development  Devel node access (devel_node_access)  Module  Disabled  8.x-1.x-dev
```

Trigger for this PR is Aegir (provision) platform verify which should parse the YAML files itself. Currently some things are hardcoded

- [ ] Directory to scan for. How should this be done
- [ ] Project type is 'core' as we don't now beforehand what is in. Should that be different?
- [ ] Version is 8.x as is only adds YAML file reads.
- [ ] Needs tests.