README.md: explain that Bin/ and Src are copies, minor editing

README.md

-# COLIBRI #
+# COLIBRI
 
+## Special directories
+
+`Bin/` and `Src/` directories are copied from their respective
+repositories using the `release_colibri_opensource.sh` script found in
+`gatel/Src`'s original repository. They should be considered read-only
+here.
+
+## Bundle
 
 In order to create a bundle of everything needed to run COLIBRI. run
 `./compile_colibri.sh` then run `./bundle.sh` it will create
 a relocalisable directory `bundle`.
 
+## Compilation on linux
 
-# Compilation on linux #
- The up-to-date information could be found in `.gitlab-ci.yml`.
+The up-to-date information could be found in `.gitlab-ci.yml`.
 
-# Compilation on windows #
- The compilation is helped by using
- https://fdopen.github.io/opam-repository-mingw/ , it will install ocaml
- compiler but also mingw for the C part. Use ocaml-env to setup the environement
- for the compilation. Then the compilation is the same than for linux.
+## Compilation on windows
 
-# LICENCE
+The compilation is helped by using
+https://fdopen.github.io/opam-repository-mingw/, it will install ocaml
+compiler but also mingw for the C part. Use ocaml-env to setup the
+environement for the compilation. Then the compilation is the same
+than for linux.
+
+## LICENCE
 
 This is the open-source colibri distribution.
 This software under the LGP2.1 LICENCE.
+