Add a new block that can be nested or ability for Query Block to be nested

[mogmarsh]

Description

I would like a block that can be nested inside a Query block that has its own settings and can operate separately from the outer block.

Use Case

On a homepage, the top story may have several optional related stories, such as in this screenshot from NYP.

The number of stories shown here, should be set without modifying the layout of the outer block and without modifying where pinned posts appear.

|----------------------------------------------------------|
|                                                          |
|           Pinned Story in Outer Block                    |
|                                                          |
|----------------------------------------------------------|
||---------------------------------------------------------|
||                                                        ||
||          New Inner Block With Independent Settings     ||
||          Could contain variable number of              ||
||          backfilled or pinned posts                    ||
||---------------------------------------------------------|
|----------------------------------------------------------|
|----------------------------------------------------------|
|                                                          |
|           Pinned Story in Outer Block                    |
|                                                          |
|----------------------------------------------------------|
|----------------------------------------------------------|
|                                                          |
|           Backfilled Story in Outer Block                |
|                                                          |
|----------------------------------------------------------|

For example, changing the number of posts shown in the inner block, would not affect the placement and which story is shown after it.