Initial work on new ant number headers task for dev site.
Work on new ant number headers task for devsite. LRDOCS-1072.
Removing header added to a markdown file.
Rebuild and deploy of liferay-doc-utils.jar after implementing new ant number headers task.
Ran ant number-headers on learning-paths.
Revert "Ran ant number-headers on learning-paths." Will number these just
before the beta release.

This reverts commit fa11c6726283fb2f2478c123570ae8c867ebfea1.
Add doc.type property for namespacing the header ID
Use doc.type in numbering headers, added clean-dist target, added number-headers and clean-dist as dependencies for prepare-dist .