Reorganize the developer's main page

This reorganizes the developer's main page by adding a
'Commands and API References' section at the same level
as the sections for Administrator's & Developer's guides.

It also removes subsections like 'Introduction' and 'Overview'
that didn't make sense any more since they included more than
one might expect from such sections.

Change-Id: Ibf5415d946238ffadedc36c9a731f773f4fa2d71

doc/source/index.rst

@@ -16,7 +16,7 @@ VM, and so on), then Ironic may be thought of as a *hypervisor API* gluing
 together multiple drivers, each of which implement some portion of that
 functionality with respect to physical hardware.
 
-The developer documentation provided here is continually kept up-to-date based
+The documentation provided here is continually kept up-to-date based
 on the latest code, and may not represent the state of the project at any
 specific prior release.
 
@@ -25,11 +25,8 @@ notes`_.
 
 .. _the release notes: http://docs.openstack.org/releasenotes/ironic/
 
-Admin Guide
-===========
-
-Overview
---------
+Administrator's Guide
+=====================
 
 .. toctree::
   :maxdepth: 1
@@ -44,19 +41,18 @@ Overview
   deploy/troubleshooting
   Release Notes <http://docs.openstack.org/releasenotes/ironic/>
 
-Commands
---------
+Commands and API References
+===========================
 
 .. toctree::
   :maxdepth: 1
 
   cmds/ironic-dbsync
+  webapi/v1
+  dev/drivers
 
-Developer Guide
-===============
-
-Introduction
-------------
+Developer's Guide
+=================
 
 .. toctree::
   :maxdepth: 1
@@ -65,25 +61,10 @@ Introduction
   dev/states
   dev/contributing
   dev/code-contribution-guide
-
-.. toctree::
   dev/dev-quickstart
   dev/vendor-passthru
-
-.. toctree::
-  :maxdepth: 1
-
   dev/faq
 
-API References
---------------
-
-.. toctree::
-  :maxdepth: 1
-
-  webapi/v1
-  dev/drivers
-
 Indices and tables
 ==================