Add zuul:value xref

Use it and zuul:attr xrefs.

Change-Id: I5cac10bbf76b54d0f035cc7c69e9304a2e197303
diff --git a/doc/source/user/config.rst b/doc/source/user/config.rst
index 7aa1a84..5ca8677 100644
--- a/doc/source/user/config.rst
+++ b/doc/source/user/config.rst
@@ -138,8 +138,6 @@
 
       There are currently two schemes for managing pipelines:
 
-      .. _independent_pipeline_manager:
-
       .. zuul:value:: independent
 
          Every event in this pipeline should be treated as independent
@@ -158,8 +156,6 @@
          pipeline. In that case, the changes have already merged, so
          the results can not affect any other events in the pipeline.
 
-      .. _dependent_pipeline_manager:
-
       .. zuul:value:: dependent
 
          The dependent pipeline manager is designed for gating.  It
diff --git a/doc/source/user/gating.rst b/doc/source/user/gating.rst
index 3398892..c1d04a7 100644
--- a/doc/source/user/gating.rst
+++ b/doc/source/user/gating.rst
@@ -41,7 +41,7 @@
 developers to create changes at a rate faster than they can be tested
 and merged.
 
-Zuul's :ref:`dependent pipeline manager<dependent_pipeline_manager>`
+Zuul's :value:`dependent pipeline manager<pipeline.manager.dependent>`
 allows for parallel execution of test jobs for gating while ensuring
 changes are tested correctly, exactly as if they had been tested one
 at a time.  It does this by performing speculative execution of test