exercise 6.2

Squashed commit of the following:

commit 5afdf0645a3d25a6fc7f8eb895fd299893c17ab7
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Fri Nov 21 14:45:50 2014 +0100

    exercise annotations

commit 1d12643005d1d870c3601d6d884c573eab8a39c5
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Fri Nov 21 14:39:16 2014 +0100

    exercise 6.2

commit cc3f40108dae20a53645426c2d9b554cfbfe4eee
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Fri Nov 21 14:30:44 2014 +0100

    finish composable commands

commit e26fdcc13c09943f1f0e3471f132090244f416f4
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Thu Nov 20 16:56:11 2014 +0100

    composable subcommands WIP

commit 26052f9da4dccc93ef7d6b3f134da838323180e3
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Wed Nov 19 18:26:50 2014 +0100

    fix Store in Liveness

commit 17abaf71de76838c9d74780d86cd787d5e06fbca
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Wed Nov 19 14:08:04 2014 +0100

    rename domains to May/Must, fix Pos/Neg and do subexpr in ConstProp, fix Worklist dependencies

commit 1945b3f755135c1dae6e8074f3cff0a54c51c708
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Tue Nov 18 18:35:27 2014 +0100

    functorized map domain

commit 7a610a1a86385fcd1889cb94cf66247709fa3f5e
Author: Ralf Vogler <ralf.vogler@gmail.com>
Date:   Mon Nov 17 18:47:23 2014 +0100

    const prop