inform the user how to set up a calnet-enabled admin after installation

The main issue was that we should inform the user how to set up a calnet-enabled admin after installation. Our we now link them to the correct anchor in the readme.md in the master github repo.

To get this message to display correctly on a vanilla D7 site I had to require that the user disables overlay.

https://jira.berkeley.edu/browse/OPENUCB-254?focusedCommentId=184981&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-184981