Issue 5521 - Restructure CMS documentation to make it easier to use and extend

docs/usage/test-server.md

Index: docs/usage/test-server.md
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+# Running the test server #
+
+The test server will convert your content directory on the fly, your changes
+will become visible immediately. To run it you need:
+
+* Python 2.7
+* [Jinja2](http://jinja.pocoo.org/) and
+  [Markdown](https://pypi.python.org/pypi/Markdown) modules (can be installed by
+  running `easy_install Jinja2 Markdown` from the command line)
+* A current copy of the
+  [cms repository](https://github.com/adblockplus/cms/) (can be
+  [downloaded as ZIP file](https://github.com/adblockplus/cms/archive/master.zip)
+  or cloned via `git clone https://github.com/adblockplus/cms.git`)
+
+Optionally, the [Werkzeug](http://werkzeug.pocoo.org/) module can be installed
+as well, this will provide some developer features.
+
+Run the `runserver.py` script from your content directory, e.g.:
+
+    python ../cms/runserver.py
+
+Alternatively, the content directory could also be specified as command line
+parameter of `runserver.py`. This will start a local web server on port 5000,
+e.g. the page the page `pages/example.md` will be accessible under
+`http://localhost:5000/en/example`.
+
+Note that the test server is inefficient and shouldn't be run in production.
+There you should generate static files as explained in the next guide,
+[Generating Static Files](generate-static-files.md).