Merge pull request #398 from laurenrother/master

Finishes the initial setup of the PE modules page.
[DOC-786] Links to appropriate PE multi-master guide

The existing document for deploying multiple masters works only for open source Puppet. This change updates the "open source only" notice to add links to the portions of the PE manual detailing how to perform a split install then add ActiveMQ and master resources as needed.
link fixes to multiple pages to fix links to console_auth.
Fix broken link in rbac_intro.md

Typo: /. instead of ./
(DOC-1368) fixing lowercase pe
Fixed example user email address in RBAC Permissions.
(DOC-1369) changing pg subtitle due to identical headings/anchors
(DOC-1367)  needs to be in ,
and if it is just set in [master] it will cause the upgrader to fail
Update link for enabling the Red Hat Optional channel.
Creates landing page for /forge.

Creates a landing page, consisting of a series of links to Forge and module related documentation, for /forge.