rearranging a few docs and small updates

doc/development/tutorials/index.rst

@@ -9,7 +9,6 @@ Refer to the following tutorials to get started with extension development.
    :caption: General extension tutorials
 
    overview
-   builders
 
 .. toctree::
    :caption: Directive tutorials
@@ -18,9 +17,3 @@ Refer to the following tutorials to get started with extension development.
    helloworld
    todo
    recipe
-
-.. toctree::
-   :caption: Theming
-   :maxdepth: 1
-
-   theming-dev