Prepared documentation

to differentiate between dev and user documentation

src/site/markdown/configuration.md.vm

 #set($h1 = '#')
 #set($h2 = '##')
+#set($h3 = '##')
 
-$h1 Configuration
+$h1 User Documentation
+
+$h2 Configuration
 
 The configuration file is a [YAML](https://en.wikipedia.org/wiki/YAML) document.
 
@@ -30,16 +33,16 @@ random:
 
 The configuration file sections are explained next.
 
-$h1 Configuration Sections
+$h2 Configuration Sections
 
-$h2 Input
+$h3 Input
 
 ```
 input:
   name: data/input.csv
 ```
 
-$h2 Output
+$h3 Output
 
 ```
 output:
@@ -48,7 +51,7 @@ output:
     name: output.csv
 ```
 
-$h2 Random
+$h3 Random
 
 ```
 random:

src/site/markdown/devindex.md.vm

+#set($h1 = '#')
+#set($h2 = '##')
+
+$h1 Developer Documentation

src/site/markdown/index.md.vm

 #set($h1 = '#')
 #set($h2 = '##')
 
-$h1 Introduction
+$h1 User Documentation
+
+$h2 Introduction
 
 This program creates individual codes for a list of input data (e.g. customers identifiers) and writes this codes to
 a csv file. Additionally barcodes for the individual codes can be created.
 
-$h1 Configuration
+$h2 Configuration
 
 The application is configured with a single configuration file.
 

src/site/site_en.xml

@@ -33,6 +33,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
       <item href="configuration.html" name="Configuration"/>
     </menu>
 
+    <menu name="Developer Documentation">
+      <item href="devindex.html" name="Introduction"/>
+    </menu>
+
     <menu ref="reports"/>
 
   </body>