Add Hiera namespace with YAML content model

Will be used to store Hiera data for labs projects,
in the form of pages Hiera:<project-name>. Only
people with projectadmin on that particular project
can edit the page, but everyone else can view it.

Also update version of Spyc in use.

Change-Id: If26ba0fcb2f58fd1963b97e807aa57e5bbe3d4c7
(cherry picked from commit 0d1eb850727180de93ad33ed9b10a9a59e59ae19)