Based on this post, I created a subclass of RecyclerView.Adapter that supports an arbitrary number of headers and footers.
https://gist.github.com/mheras/0908873267def75dc746
Although it seems to be a solution, I also think this thing should be managed by the LayoutManager. Unfortunately, I need it now and I don't have time to implement a StaggeredGridLayoutManager from scratch (nor even extend from it).
I'm still testing it, but you can try it out if you want. Please let me know if you find any issues with it.
