Manager added, translation animation available

AnimationManager added, it encapsulate osgAnimation::... ， makes it easy
to do animation.
Three steps to use it :
1. set root scene node
"AnimationManager::singleton()->setRootSenceNode(root)"
2. give the "osg::MatrixTransform"node you want to animate
"AnimationManager::singleton()->addAnimationNode(animDoor)"
3. set the animation way you want,
"AnimationManager::singleton()->setTranslatePath4Node(animDoor,
vertices)"
4. start the animation,
"AnimationManager::singleton()->playAnimation4Node(animDoor)"