Add CLI documentation

docs/cli.markdown

@@ -0,0 +1,39 @@
+Command Line Interface
+======================
+
+Kanboard provide a simple command line interface that can be used from any Unix terminal.
+
+This feature is useful to run commands outside the web server by example a huge report.
+
+Actually there is only one command, more stuff will be added later.
+
+Usage
+-----
+
+- Open a terminal and go to your Kanboard directory (example: `cd /var/www/kanboard`)
+- Run the command `./kanboard`
+
+```bash
+$ ./kanboard
+Kanboard command line interface
+===============================
+
+- Task export to stdout (CSV format): ./kanboard export-csv <project_id> <start_date> <end_date>
+```
+
+Available commands
+------------------
+
+### CSV export of tasks
+
+Usage:
+
+```bash
+./kanboard export-csv <project_id> <start_date> <end_date>
+```
+
+Example:
+
+```bash
+./kanboard export-csv 1 2014-07-14 2014-07-20 > /tmp/my_custom_export.csv
+```