[gnome-builder] doc: prefer "Extension" over "Plugin"

[Christian Hergert <chergert src gnome org>]

commit 156e28d99c244b2ef37961b4d9e509660f588014
Author: Christian Hergert <chergert redhat com>
Date:   Wed Sep 6 14:32:12 2017 -0700

    doc: prefer "Extension" over "Plugin"

 doc/plugins/creating.rst |   22 ++++++++++++----------
 doc/plugins/index.rst    |    8 ++++----
 2 files changed, 16 insertions(+), 14 deletions(-)
---
diff --git a/doc/plugins/creating.rst b/doc/plugins/creating.rst
index da5ff6c..7809a27 100644
--- a/doc/plugins/creating.rst
+++ b/doc/plugins/creating.rst
@@ -1,19 +1,21 @@
-##########################
-Creating Your First Plugin
-##########################
+#############################
+Creating Your First Extension
+#############################
 
 Plugins consist of two things.
-First, a meta-data file describing the plugin which includes things like a name, the author, and where to 
find the plugin.
-Second, the plugin code which can take the form of a shared library or python module.
+First, a meta-data file describing the extension which includes things like a name, the author, and where to 
find the extension.
+Second, the code which can take the form of a shared library or python module.
 
-Builder supports writing plugins in C, C++, Vala, or Python.
+Builder supports writing extensions in C, Vala, or Python.
 We will be using Python for our examples in this tutorial because it is both succinct and easy to get 
started with.
 
-First, we will look at our plugin meta-data file.
+First, we will look at our extension meta-data file.
 The file should have the file-suffix of ".plugin" and it's format is familiar.
-It starts with a line containing "[Plugin]" indicating this is plugin meta-data.
+It starts with a line containing "[Plugin]" indicating this is extension metadata.
 Then it is followed by a series of "Key=Value" key-pairs.
 
+.. note:: We often use the words "extension" and "plugin" interchangeably.
+
 .. code-block:: ini
 
    # my_plugin.plugin
@@ -51,8 +53,8 @@ The first is called ``do_load`` and is executed when the extension should load.
 And the second is called ``do_unload`` and is executed when the plugin should cleanup after itself.
 Each of the two functions take a parameter called ``application`` which is an ``Ide.Application`` instance.
 
-Loading our Plugin
-==================
+Loading our Extension
+=====================
 
 Now place the two files in ``~/.local/share/gnome-builder/plugins`` as ``my_plugin.plugin`` and 
``my_plugin.py``.
 If we run Builder from the command line, we should see the output from our plugin!
diff --git a/doc/plugins/index.rst b/doc/plugins/index.rst
index c1475f5..53dc938 100644
--- a/doc/plugins/index.rst
+++ b/doc/plugins/index.rst
@@ -1,12 +1,12 @@
 .. _creating_plugins:
 
-#######
-Plugins
-#######
+##########
+Extensions
+##########
 
 The following provides examples of various ways you can extend Builder.
 All examples are provided in the Python 3 language for succinctness and clarity.
-You may also chooser to implement plugins in C or Vala.
+You may also chooser to implement extensions in C or Vala.
 
 .. toctree::
    :maxdepth: 3