Formats tidy

Addressing the couple of points on ticket 11223 for the Model & Formats docs and general tidying of the schema changes pages after comments by @mtbc re: formatting especially of bulleted lists.

Wider tidy and reorganisation is also needed but I thought this was enough to review in one go!

N.B. Formats docs on dev_4_4 are basically now legacy which is why I've done this straight to develop.