add ep_headings option to etherpad install

Make it possible to optionally install ep_headings on an etherpad
environment. This makes it easy to enable this on some environments,
but not all. Default to 'false', but set 'true' for etherpad_dev.

With summit coming up, it would be nice to have ep_headings in the
etherpads, makes them a lot easier to read.

fix puppet lint issue with all the equals signs not lining up.

Change-Id: I8cfa12480aed0b351012161c2cdbc406c0f52e7a
Reviewed-on: https://review.openstack.org/26380
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Paul Belanger <paul.belanger@polybeacon.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins