DOCS-487 revert Aggregation sign-post

Author: Bob Grabar

source/aggregation.txt

@@ -4,32 +4,19 @@
 Aggregation
 ===========
 
-The :ref:`Aggregation framework <aggregation-framework>` provides
+Aggregation provides
 a natural method for aggregating data inside of MongoDB.
 
-Documentation
--------------
+For a description of MongoDB aggregation, see
+:doc:`/applications/aggregation`. For examples of aggregation, see
+:doc:`/tutorial/aggregation-examples`. For descriptions of aggregation
+operators, see :doc:`/reference/aggregation`.
 
-The following document describes MongoDB aggregation:
+The following is the outline of the aggregation documentation:
 
 .. toctree::
    :maxdepth: 3
 
    applications/aggregation
-
-Tutorial
----------
-
-The following tutorial provides examples of aggregation operations:
-
-.. toctree::
-   :maxdepth: 1
-
    tutorial/aggregation-examples
-
-Reference
----------
-
-The following reference section describes aggregation operators:
-
-- :doc:`/reference/aggregation`
+   reference/aggregation