[OCaml version] down-bootstrapping, up-bootstrapping work. However, the bootstrapping can fail as some depending packages are not compatible with 3.11.2 for instance.
[OCaml version] down-bootstrapping, up-bootstrapping work.
However, the bootstrapping can fail as some depending packages are not compatible with 3.11.2 for instance.

In detail :
- fix the wrong path installation of OCaml
- automatically install conf-ocaml when "opam switch"

Future works :
- some documentations are installed in $OVERSION/man instead of $OVERSION/doc
- fail when we attempt to install an already existing name (e.g. $OVERSION/lib/ocaml)

abate/opam,abate/opam