added information about built in plugins

docs/plugins/overview.rst

 Plugins
 =======
+*tantum. CMS* is extendable through plugins. Those go into the ``plugins``
+directory and have to choose a plugin namespace.
 
+By default, *tantum. CMS* comes with the following plugins:
+
+* ``DynamicTitle``
+* ``BlogRoll``
+
+DynamicTitle
+------------
+This plugin enables support for "subtitles" in the websites HTML ``<title>``
+tag. It prepends the name of the Website with the name of the current page,
+separated by a long dash (``–``).
+
+.. note::
+	**Example:**
+
+	Imprint – tantum. CMS
+
+BlogRoll
+--------
+The *BlogRoll* plugin provides a Weblogesque functionality. If a folder inside
+the ``webroot`` folder contains subfolders, and those subfolders do all have a
+numerical name (``1``, ``2``, and so on), the plugin deems that page a weblog.
+It chooses a special template and adds *"newer posts"*/*"older posts"* links to
+the bottom.
+
+The following folder structure will give you a simple blog with two pages of
+backlog:
+
+* ``webcontents/``
+	* ``Blog/``
+		* ``1/``
+		* ``2/``
+		* ``My first blog post.md``
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