Mohamed Hernouf

This PR impose bundled opam to use mccs solver. This is because of more descriptive error message when there is a lack on some system dependencies.

This PR fixes filter creation, in order to take correct constraint about pinned package's version. This avoids choosing package from repository and further inconsistent dependencies' resolution.

It will be really great if `opam-bundle` would perform some checks about correctness of specified ocaml or opam version before bundle construction.