add pareto multiopt
[Issue#190] add test + CHANGES.md
[Issue #191] first step, deal with integer

+ set default trail env. to FLAT (faster)
[Issue #191] second step: trail env.

- next step: copy
[Issue #191]: fix buildFakeFactory
[Issue #191]: change the way bipartite set is managed

- creation of BasicIndexedBipartiteSet, more simple which includes offset
remove useless data structures
[Issue #191] start copy env
[Fix #191] Env. Copying
Merge with feature-pareto