Rough Minimax Implementation

Cleaning code pending.
Added gitIgnore who got lost.
Refactored undo redo

Moved undo redo functionnality out of RevGame
BoardGame now has access to an ISnapshotContainer to make available this
functionnality.

Minimax is currently not available in the user interface but will be
soon.
Merge pull request #1 from cslecours/MinimaxImplementation

Merge