Plugins doc + minor design changes.

docs/plugins.rst

@@ -0,0 +1,75 @@
+.. _plugins:
+
+Plugins
+#######
+
+Since version 2.8, pelican manages plugins. Plugins are a way to add feature to
+pelican without having to directly hack pelican code.
+
+Pelican is shipped with a set of core plugins, but you can easily implement
+your own (and this page describes how)
+
+How to use plugins?
+====================
+
+To load plugins, you have to specify a them in your settings file. You have two
+ways to do so:  by specifying strings with the path to the callables: ::
+
+    PLUGINS = ['pelican.plugins.gravatar',] 
+
+Or by importing them and adding them to the list::
+
+    from pelican.plugins import gravatar
+    PLUGINS = [gravatar, ]
+
+If your plugins are not in an importable path, you can specify a `PLUGIN_PATH`
+in the settings::
+
+    PLUGIN_PATH = "plugins"
+    PLUGINS = ["list", "of", "plugins"]
+
+How to create plugins?
+======================
+
+Plugins are based on the concept of signals. Pelican sends signals and plugins
+subscribe to those signals. The list of signals are defined in a following
+section.
+
+The only rule to follow for plugins is to define a `register` callable, in
+which you map the signals to your plugin logic. Let's take a simple exemple::
+
+    from pelican import signals
+
+    def test(sender):
+        print "%s initialized !!" % sender
+
+    def register():
+        signals.initialized.connect(test)
+
+
+List of signals
+===============
+
+Here is the list of currently implemented signals:
+
+=========================   ============================   =====================
+Signal                      Arguments                      Description
+=========================   ============================   =====================
+initialized                 pelican object
+article_generate_context    article_generator, metadata
+=========================   ============================   =====================
+
+The list is currently small, don't hesitate to add signals and make a pull
+request if you need them!
+
+List of plugins
+===============
+
+Not all the list are described here, but a few of them have been extracted from
+pelican core and provided in pelican.plugins. They are described here:
+
+Tag cloud
+---------
+
+Translation
+-----------