Rename Witan module into Colibri2

Makefile

TODO

colibri2.opam

compare_smt2.sh

dune-project

misc/header.txt

misc/header_witan.txt

src/core/colibri2_core.ml

src/core/demon.ml

src/core/demon.mli

src/core/dune

src/core/egraph.ml

src/core/egraph.mli

src/core/events.ml

src/core/events.mli

src/core/interp.ml

src/core/structures/domKind.ml

src/core/structures/dune

src/core/structures/expr.ml

src/core/structures/nodes.ml