Add more dunder dict docs per @cachedout

There are still a few esoterics to get in from some of the backend
module systems, but these are the big ones

doc/topics/development/dunder_dictionaries.rst

@@ -8,6 +8,80 @@ others. This document will describe each dictionary and detail where they exist
 and what information and/or functionality they provide.
 
 
+__opts__
+--------
+
+Available in
+~~~~~~~~~~~~
+
+- All loader modules
+
+The ``__opts__`` dictionary contains all of the options passed in the
+configuration file for the master or minion.
+
+.. note::
+
+    In many places in salt, instead of pulling raw data from the __opts__
+    dict, configuration data should be pulled from the salt `get` frunctions
+    such as config.get, aka - __salt__['config.get']('foo:bar')
+    The `get` functions also allow for dict traversal via the *:* delimiter.
+    Consider using get functions whenever using __opts__ or __pillar__ and
+    __grains__ (when using grains for configuration data)
+
+The configuration file data made available in the ``__opts__`` dictionary is the
+configuration data relative to the running daemon. If the modules are loaded and
+executed by the master, then the master configuration data is available, if the
+modules are executed by the minion, then the minion configuration is
+available. Any additional information passed into the respective configuration
+files is made available
+
+__salt__
+--------
+
+Available in
+~~~~~~~~~~~~
+
+- Execution Modules
+- State Modules
+- Returners
+
+``__salt__`` contains the execution module functions. This allows for all
+functions to be called as they have been set up by the salt loader.
+
+.. code-block:: python
+
+    __salt__['cmd.run']('fdisk -l')
+    __salt__['network.ip_addrs']()
+
+__grains__
+----------
+
+Available in
+~~~~~~~~~~~~
+
+- Execution Modules
+- State Modules
+- Returners
+- External Pillar
+
+The ``__grains__`` dictionary contains the grains data generated by the minion
+that is currently being worked with. In execution modules, state modules and
+returners this is the grains of the minion running the calls, when generating
+the external pillar the ``__grains__`` is the grains data from the minion that
+the pillar is being generated for.
+
+__pillar__
+-----------
+
+Available in
+~~~~~~~~~~~~
+
+- Execution Modules
+- State Modules
+- Returners
+
+The ``__pillar__`` dictionary contains the pillar for the respective minion.
+
 __context__
 -----------