GatewayDest: allow noWrapper mode

[slorber]

GatewayDest should be able to render components in place without the need to add a wrapper element.

My usecase for this is my GatewayDest is inside a container with align-items: space-between. Having an empty wrapper View here messes up my layout. (It's for a dynamic RN dev toolbar menu)

Also, I think not having a wrapper could be a nice default, and make react-gateway work out of the box with RN. If the user wants to wrap his dest he could still do that in userland.

But that would be a breaking change and require minimum React version to work.

[slorber]

Actually, just found out that it's possible to do this, so actually it's possible to opt-out of the wrapper from userland.

Still, I think it would make sense to use fragment as a default and would like your opinion on that.