Drush deregister improvements

[paul-m]

Fixes [issue#]

Describe your changes

Modifies drush dkan:harvest:deregister:

• Adds a confirmation step ('Are you sure?'). Can be bypassed with -y, --yes, or --no-interaction.
• Adds a flag to the command line, --revert. This will revert all datasets in the harvest before deregistering, and is the equivalent of drush dkan:harvest:revert ID && drush dkan:harvest:deregister ID

QA Steps

• Add manual QA steps in checklist format for a reviewer to perform. Be as specific as possible, provide examples if appropriate.

Checklist before requesting review

If any of these are left unchecked, please provide an explanation

• I have updated or added tests to cover my code
• I have updated or added documentation

[janette]

Let's define this a little more on line 121.

Deregister a harvest. This action removes the harvest plan from the system, but will leave the datasets in place. This is good if you are using harvest to migrate content and you do not plan on using the harvest feature to update the datasets.
If you want to remove the harvest plan AND the datasets associated with it, use the --revert option.

[janette]

Also update the dkan:harvest:revert description

Revert a harvest, i.e. remove harvested entities and unpublish orhpaned keywords, themes, and distributions. The harvest plan will remain and can be run again to generate the datasets after any issues have been resolved.