Create a page of drivers with stevedore.sphinxext

As per:
http://lists.openstack.org/pipermail/openstack-dev/2015-August/073338.html

The point behind the addition of the stevedore.sphinxext extension is
"to document drivers and other types of plugins to make the available
sets built into projects easier to discover" (dhellman).

Change-Id: I8427398e8d01c36f346e493a8144c1012ca7c5bf

doc/source/conf.py

@@ -33,6 +33,7 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.ifconfig',
               'sphinx.ext.graphviz',
               'oslosphinx',
+              'stevedore.sphinxext'
               ]
 
 # autodoc generation is a bit aggressive and a nuisance

doc/source/database_architecture.rst

@@ -0,0 +1,9 @@
+==============================
+ Cinder Database Architecture
+==============================
+
+Cinder Database Backends
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. list-plugins:: cinder.database.migration_backend
+    :detailed:

doc/source/drivers.rst

@@ -0,0 +1,6 @@
+===================
+ Available Drivers
+===================
+
+.. list-plugins:: oslo_messaging.notify.drivers
+    :detailed:

doc/source/index.rst

@@ -41,6 +41,11 @@ Developer Docs
    :maxdepth: 1
 
    devref/index
+   database_architecture
+   scheduler-filters
+   scheduler-weights
+   drivers
+   oslo-middleware
 
 API Extensions
 ==============

doc/source/oslo-middleware.rst

@@ -0,0 +1,6 @@
+==========================
+ Oslo Middleware
+==========================
+
+.. list-plugins:: oslo_middleware
+    :detailed:

doc/source/scheduler-filters.rst

@@ -0,0 +1,6 @@
+==============================
+ Cinder Scheduler Filters
+==============================
+
+.. list-plugins:: cinder.scheduler.filters
+    :detailed:

doc/source/scheduler-weights.rst

@@ -0,0 +1,6 @@
+==========================
+ Cinder Scheduler Weights
+==========================
+
+.. list-plugins:: cinder.scheduler.weights
+    :detailed: