Documentation: Clearer structure on front page

Divides 'User Guide' topics into different kinds of users, End Users,
Project Owners / Power Users and Administrators. This is the first
change in a coming series that will rework the structure of the
documentation.

This will probably make new users feel more welcomed, as they won't
have to see the most advanced topics to begin with.

Change-Id: Ia11c82c69e0ff2b42d106e631adf2c31a7135ad8
Signed-off-by: Fredrik Luthander <fredrik.luthander@sonymobile.com>

Documentation/index.txt

@@ -6,27 +6,36 @@ Getting Started
 
 * link:intro-quick.html[A Quick Introduction To Gerrit]
 
-User Guide
+End User Guide
-----------
+--------------
 
-* link:http://source.android.com/submit-patches/workflow[Default Workflow]
+* External link: link:http://source.android.com/submit-patches/workflow[Default Android Workflow]
 * link:user-search.html[Searching Changes]
 * link:cmd-index.html[Command Line Tools]
-* link:pgm-index.html[Server Programs]
 * link:user-upload.html[Uploading Changes]
 * link:user-changeid.html[Change-Id Lines]
 * link:user-signedoffby.html[Signed-off-by Lines]
-* link:access-control.html[Access Controls]
 * link:error-messages.html[Error Messages]
+* link:user-notify.html[Subscribing to Email Notifications]
+
+Project Owner and Power User Guide
+----------------------------------
+
+* link:access-control.html[Access Controls]
 * link:rest-api.html[REST API]
 * link:user-dashboards.html[Dashboards]
-* link:user-notify.html[Subscribing to Email Notifications]
 * link:user-submodules.html[Subscribing to Git Submodules]
 * link:prolog-cookbook.html[Prolog Cookbook]
 * link:prolog-change-facts.html[Prolog Facts for Gerrit Changes]
+* link:config-labels.html[Review Labels]
+
+Admin User Guide
+----------------
+
+* link:pgm-index.html[Server Programs]
 
 Installation
-------------
+~~~~~~~~~~~~
 
 * link:licenses.html[Licenses and Notices]
 * link:install.html[Installation Guide]
@@ -34,7 +43,7 @@ Installation
 * link:project-setup.html[Project Setup]
 
 Configuration
--------------
+~~~~~~~~~~~~~
 
 * link:config-gerrit.html[System Settings]
 * link:config-contact.html[User Contact Information]
@@ -45,16 +54,15 @@ Configuration
 * link:config-hooks.html[Hooks]
 * link:config-mail.html[Mail Templates]
 * link:config-cla.html[Contributor Agreements]
-* link:config-validation.html[Commit Validation]
-* link:config-labels.html[Review Labels]
 
-Developer Documentation
+Gerrit Developer Documentation
------------------------
+------------------------------
 
 * link:dev-readme.html[Developer Setup]
 * link:dev-eclipse.html[Eclipse Setup]
 * link:dev-contributing.html[Contributing to Gerrit]
 * link:dev-plugins.html[Developing Plugins]
+* link:config-validation.html[Commit Validation]
 * link:dev-design.html[System Design]
 * link:i18n-readme.html[i18n Support]
 * link:dev-release.html[Developer Release]