Remove coercion `iMsg_car` and `Proper` instances to avoid one accidentally breaking the `iMsg` abstraction.

- Protocols are no longer contractive in the message
- New type `iMsg` for messages to avoid telescopes in protocols
- Better rules for subprotocols that do not involve telescopes, but allow introduction
  and elimination of quantifiers and the payload
- Better notations for protocols
- Notation ⊑ for subprotocols
- Make ⊑ except-0 so one can strip laters when proving a ⊑
- Restore recursive domain equation to push later inwards to support protocols
  that are not contractive in the mssage.
- Proofmode support for easy manipulation of ⊑

Kinded subtyping, better file structure, more setoid stuff, reorganize imports.

By moving the later further to the outside, we can kill many occurences
of `Next`, and get rid of laters/except_0s at awkward positions. Also we
can have a sensible eliminator `proto_elim`.

Moved Iris specific stuff into a utility file.

TODO: fix in-place merge function.

- Allow for binders in protocols.
- Model protocols in CPS style using the COFE solver.
- Change the channel methods so they do not mention sides.
- Lots of refactoring.
- Generalize the `list_sort` example.
- Move stuff to stdpp/Iris.

- Put code and proofs of examples in a single file.
- Rename encode/decode to avoid conflicts with encode/decode (of the countable class) in stdpp.
- Remove useless imports.

commit 32f5885b5083c6052251a266b0ec4b6f0cd01bcc
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue Jun 11 11:54:32 2019 +0200

    Full bump

commit 3fdf913129ee6c1081e947de48e71ca6411f33da
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Tue Jun 11 11:31:22 2019 +0200

    More cleanup.

commit 46be8c0184d5a9e7de42022e389e23df99f73f6d
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Mon Jun 10 22:50:02 2019 +0200

    Some cleanup.

commit 2dc17e2cafc0b33e5ef0d2a6f6862b0938f68b18
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Mon Jun 10 16:33:46 2019 +0200

    WIP

commit 9427aa2ddd4fecb49b8e1c02eccc954fdb8af554
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Mon Jun 10 15:02:21 2019 +0200

    iRewrite Bug inspection

commit 40393f8800ab1a587f49f9ad479f5dc94b2bf2bc
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Mon Jun 10 14:56:08 2019 +0200

    Bumped Iris

commit 660218ca36e148b7270fd0044a2401fa553373d1
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Mon Jun 3 11:31:11 2019 +0200

    Add type.

commit 54214779390c19b1f9c8b293ac26f36efda95f4d
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Fri May 31 16:24:05 2019 +0200

    Coinductive version of stype.

commit b0fe9afb
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Fri May 31 13:19:13 2019 +0200

    Bump Iris.

commit a96494d62639ca14449d90c3a510c3a63a28fc07
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue May 7 18:39:41 2019 +0200

    Finalized List sort example, and introduced list encodings

commit 1b9fc4de897a5ea15c0e9a11b4ace407adda02ad
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Fri May 3 15:28:21 2019 +0200

    WIP List sort example

commit 4ce5eb98585f25daa6b5682cdc6ab34a192f2b69
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Fri May 3 11:18:07 2019 +0200

    WIP list sort example

Squashed commit of the following:

commit b404feb30cecf7678c0ad6007171a13361483086
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Wed Apr 17 17:36:21 2019 +0200

    Bumped try_recv and recv to ofe st's

commit 4aa2399d02de67feacdcba9d0929cd7e20a1f7da
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Wed Apr 17 15:19:14 2019 +0200

    Finalised send proof

commit ae9857fcf8a88e917b6ccb219ac6e27a1afe46e2
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Wed Apr 17 14:58:34 2019 +0200

    Tweak.

commit 4d86571d9d51992d6ee83fdfbbfbec24ce8fdbc8
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Wed Apr 17 14:54:44 2019 +0200

    Work.

commit 0fedd453c2ce41862f0a2040294ad0d271e39e85
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Wed Apr 17 12:55:52 2019 +0200

    Bumped Robbert feedback, WIP send st triple

commit f5672f9a529699ca0610329d32c59ad33d3146de
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue Apr 16 14:43:52 2019 +0200

    WIP

commit ef354c3899e796ccb091e1275e8b44d12a3393fd
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue Apr 16 13:39:41 2019 +0200

    Lifted stype over OFEs. Fixed residuals in channel.v

commit 1a47979d7497adb8c14ac9b57caf5632383ef2c3
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue Apr 16 13:08:28 2019 +0200

    WIP

commit 605562ba86b9481ae367409c87492b61d199111f
Author: Jonas Kastberg Hinrichsen <jkas@itu.dk>
Date:   Tue Apr 16 13:05:03 2019 +0200

    Test

commit 77eb6feb071da540fbc424602628c045ea15c004
Author: Robbert Krebbers <mail@robbertkrebbers.nl>
Date:   Mon Apr 15 16:24:13 2019 +0200

    Working.