Narrative description style consistency review

When creating narrative descriptions for elements following the US Core practice, there is currently no clear guidance on the style of that description and ones that we have added for qi-core may not follow the practices followed by us core. This task will:

1. create a style guide for these descriptions based on review of us core's descriptions and potentially a discussion with the us core authors about how they approach it.
2. add that style guide to the MADFSH documentation
3. review and adjust all added narrative descriptions to meet the style recommendations