Adding `class_item` macro.
Removing "namespace.twig" template, renaming other templates.

The "namespace.twig" template is being removed as it is not really used. Plus it has the potential to cause file name conflicts with classes that share the same name as the namespace. I instead opted to use the other index templates, which have been numbered so that they can be ordered and prevent that naming conflict.
Adding some text blurb, using `class_item` macro.
class_item: Displaying short description, if available.
Adding `class_name` and `class_type`.

Modified `class_item` to re-use `class_name`.
Making it a final class.
Adding content to class info.

Added the short description, long description, and signature.