Matrix field - add option to start with callapsed block

[piotrpog]

This might sound rather counterintuitive, but bear with me.

I often use matrix block to group some fields. Such matrix fields has min and max blocks setting set to 1. And while such matrix field always starts with initial block already existing, sometimes i would rather this block be callapsed at first.

[bencresty]

+1
Having lots of blocks on a page it's easier for us / clients to always start with all blocks collapsed, so we can open only the one we wish to edit (we prefer this to be optionally per page / entry tho!)