Unpublish theme files when the theme is uninstalled.

Problem/Motivation

We unpublish content pages when nodes are deleted but not theme files when the theme is uninstalled.

Steps to reproduce

Proposed resolution

Unpublish theme files when theme is uninstalled.

Remaining tasks

• Update code
• Review and test
• Commit

User interface changes

API changes

Data model changes

Theme files will be unpublished when theme is uninstalled in Drupal.