Allow ${version} to be Expanded in Other Files

Previously, only **/index.xml has placeholders expanded.

Add an optional property (expandPlaceholders) that will
permit a project to add a comma-delimited list of
additional file patterns that will be expanded.

Spring-AMQP currently has a maven snippet including the
version in quick-tour.xml.
Tweak CSS format of <p> tags in callouts

Include spacing between paragraphs in 'tip', 'note' and 'warning'
callout sections.