Move to OASIS/Ocamlbuild (DO NOT MERGE)

PR to move build system of Ocsigen Server from Makefile to OASIS/Ocamlbuild. This is not completed.

We must choose between commandline/yes or commandline/no.
We must see whether compilation is native or not.
We must add tests Baselib.
We must add Ocsigen_cookies (as an Object in OASIS).
Compile other extensions.
Deport use ocamlfind from myocamlbuild.ml to ocsigen_loader.ml.

PS: sorry for recovery this PR in my repository.
Why ? Why META of extensions is in `src/extensions/userconf/` ? I don't known.