Drush command to see the status of the variables

Problem/Motivation

We don't have a command to see the summary of the actual status for all the variables.

Proposed resolution

We need something like this:

drush na-summary

Will show the status summary of all the variables.

Remaining tasks

None.

User interface changes

None.

API changes

Added the new drush command:

drush na-summary

Data model changes

None.