Documentation and changelog for the plugin_filtering config option

docs/docsite/rst/plugin_filtering_config.rst

@@ -0,0 +1,26 @@
+.. _plugin_filter_config:
+
+Plugin Filter Configuration
+===========================
+
+Ansible 2.5 adds the ability for a site administrator to blacklist modules that they do not want to
+be available to Ansible. This is configured via a yaml configuration file (by default,
+:file:`/etc/ansible/plugin_filters.yml`). The format of the file is:
+
+.. code-block:: YAML
+
+    ---
+    filter_version: '1.0'
+    module_blacklist:
+      # Deprecated
+      - docker
+      # We only allow pip, not easy_install
+      - easy_install
+
+The file contains two fields:
+
+* a version so that it will be possible to update the format while keeping backwards
+  compatibility in the future   The present version should be the string, ``"1.0"``
+
+* a list of modules to blacklist.  Any module listed here will not be found by Ansible when it
+  searches for a module to invoke for a task.