Add name property on registry attribute groups

[AlexanderWert]

In order to automatically render readable titles for generated attributes registry docs, it would be useful to have display names for attribute groups in the YAML files (see #917 (comment)).

Proposal is to add a property name (or display_name or title) to each attributes group in the registry so that the weaver can use that property for rendering headings.

Example:

groups:
  - id: registry.aws.dynamodb
    prefix: aws.dynamodb
    type: attribute_group
    name: AWS DynamoDB
    brief: >
            This document defines attributes for AWS DynamoDB.
    attributes:
         ...

[jsuereth]

As an FYI - in the meantime I updated the template to use the acronyms filter. This allows us to ensure things like iOS are always spelled correctly in weaver.

I still want this feature though.