OP wants multi-window stuff a la snap.
I don't think that's something that is quite ready to go since many smartphone apps won't be able to handle half the screen size easily. (webOS apps could try, since notifications could use up a variable amount of screen space, but even then, at half the screen being used, it was awkward somewhat)
I know Samsung has done it, but I believe it's only available to select apps with have been made able to do it.