Dynamic sections
I would really like to be able to create "sections" to my designs which can be placed after each other (from top to bottom). Today in Sketch, if a design change is made it often results in that you have to select all other elements and "push them down" on the page.

Functionality:
- A section consists of a unlimited number of other elements (just like a group)
- A section is dynamic in height, so if the height of the section is changed, it pushes the sections below down.
- Each section can be dragged and dropped over/under other sections to sort them from page top to bottom.
