[Misc] Explain the configuration file behavior

* Add TOC entry

README.md

@@ -12,31 +12,32 @@ As an application wiki, XWiki allows for the storing of structured data and the
 
 <!-- generated with pandoc -f gfm --toc -o readme-toc.md README.md -->
 
--	[Introduction](#introduction)
--	[How to use this image](#how-to-use-this-image)
-	-	[Pulling existing image](#pulling-an-existing-image)
-		-	[Using docker run](#using-docker-run)
-		-	[Using docker-compose](#using-docker-compose)
-		-	[Using Docker Swarm](#using-docker-swarm)
-	-	[Using an external Solr service](#using-an-external-solr-service)
-		-	[Preparing Solr container](#preparing-solr-container)
-		-	[Docker run example](#docker-run-example)
-		-	[Docker Compose example](#docker-compose-example)
-	-	[Configuring Tomcat](#configuring-tomcat)
-	-	[Building](#building)
--	[Upgrading XWiki](#upgrading-xwiki)
--	[Details for the xwiki image](#details-for-the-xwiki-image)
-	-	[Configuration Options](#configuration-options)
-	-	[Passing JVM options](#passing-jvm-options)
-	-	[Miscellaneous](#miscellaneous)
+- [Introduction](#introduction)
+- [How to use this image](#how-to-use-this-image)
+    -	[Pulling existing image](#pulling-an-existing-image)
+        -	[Using docker run](#using-docker-run)
+        -	[Using docker-compose](#using-docker-compose)
+        -	[Using Docker Swarm](#using-docker-swarm)
+    -	[Using an external Solr service](#using-an-external-solr-service)
+        -	[Preparing Solr container](#preparing-solr-container)
+        -	[Docker run example](#docker-run-example)
+        -	[Docker Compose example](#docker-compose-example)
+    -	[Configuring Tomcat](#configuring-tomcat)
+    -	[Building](#building)
+- [Upgrading XWiki](#upgrading-xwiki)
+- [Details for the xwiki image](#details-for-the-xwiki-image)
+    -	[Configuration Options](#configuration-options)
+    -	[Passing JVM options](#passing-jvm-options)
+    -	[Configuration Files](#configuration-files)
+    -	[Miscellaneous](#miscellaneous)
 - [For Maintainers](#for-maintainers)
-  - [Update Docker Images](#update-docker-images)
-  - [Testing Docker Images](#testing-docker-images)
-  - [Clean Up](#clean-up)
--	[License](#license)
--	[Support](#support)
--	[Contribute](#contribute)
--	[Credits](#credits)
+    -	[Update Docker Images](#update-docker-images)
+    -	[Testing Docker Images](#testing-docker-images)
+    -	[Clean Up](#clean-up)
+- [License](#license)
+- [Support](#support)
+- [Contribute](#contribute)
+- [Credits](#credits)
 
 # Introduction