Started documenting application

src/site/markdown/configuration.md.vm

+#set($h1 = '#')
+#set($h2 = '##')
+
+$h1 Configuration
+
+The configuration file is a [YAML](https://en.wikipedia.org/wiki/YAML) document.
+
+The sample configuration (found in `etc/barcode.yaml`) is
+
+```
+input:
+  name: data/input.csv
+output:
+  folder: output/
+  file:
+    name: output.csv
+random:
+  size: 128
+  codes:
+    -
+      type: qrcode
+      size: 120x120
+      errorcorrection: M
+      filetype: png
+      encoding: hex
+      url: https://www.example.org/{code}
+  encodings:
+    - base58
+```
+
+The configuration file sections are explained next.
+
+$h1 Configuration Sections
+
+$h2 Input
+
+```
+input:
+  name: data/input.csv
+```
+
+$h2 Output
+
+```
+output:
+  folder: output/
+  file:
+    name: output.csv
+```
+
+$h2 Random
+
+```
+random:
+  size: 128
+  codes:
+    -
+      type: qrcode
+      size: 120x120
+      errorcorrection: M
+      filetype: png
+      encoding: hex
+      url: https://www.example.org/{code}
+  encodings:
+    - base58
+```

src/site/markdown/index.md.vm

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