Move zuul layout into /etc/zuul/layout

Move the layout.yaml and functions files into a subdir of /etc/zuul
to facilitate the separation of project and system configuration.

Change-Id: Ib62063ffef91c370d4626e8590ac856177f6099f

manifests/init.pp

@@ -146,6 +146,11 @@ class zuul (
     ensure => directory,
   }
 
+  file { '/etc/zuul/layout':
+    ensure  => directory,
+    require => File['/etc/zuul'],
+  }
+
 # TODO: We should put in  notify either Service['zuul'] or Exec['zuul-reload']
 #       at some point, but that still has some problems.
   file { '/etc/zuul/zuul.conf':

templates/zuul.conf.erb

@@ -14,7 +14,7 @@ baseurl=<%= gerrit_baseurl %>
 <% end -%>
 
 [zuul]
-layout_config=/etc/zuul/layout.yaml
+layout_config=/etc/zuul/layout/layout.yaml
 log_config=/etc/zuul/logging.conf
 state_dir=/var/lib/zuul
 git_dir=/var/lib/zuul/git