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.

FIXME: UI should show 'view source' rather than 'edit'
when the user has no permission to edit the page

Change-Id: If26ba0fcb2f58fd1963b97e807aa57e5bbe3d4c7
Merge "Add Hiera namespace with YAML content model"