JIRA Importers Plugin needs to be a system plugin

Summary

Disabling the jira-importers-plugin causes the Software and Service Desk applications to disable.

Steps to Reproduce

1. Go to manage add-ons >> all add-ons
2. Disable jira-importers-plugin

Expected Results

The JIM plugin should be a system plugin and therefore not subject to being disabled.

Actual Results

The JIRA Applications become disabled, and JIM is disabled as well

Workaround

Re-enable the JIM plugin, then re-enable the other plugins, or restart.