Support hero images for pages/posts
Add support for defining a hero image for pages and blog posts.
- Add support for using images (or not)
- Add option to remove hero section on a given page/blog
- Add option to define the size of the hero section on a given page/blog
- Add option to include title/subtitle in the hero section or not
- If not including the title/subtitle in the hero section, they will be added below (this helps resolve issues with using text over coloured images)