Fixed dynamic shapes using meshes.

Fixed dynamic shapes using meshes.

[problem]      Cloth demos crash
[cause]        DynamicsShape of type mesh is using discardable meshes
[solution]     Need to ensure that the meshes used for dynamics shapes are not
               discardable. Needs a new API to create mesh actors from such a mesh.
               (Don't want to have non-discardable meshes in public API)

New API is:
Cloth cloth = Cloth::New(width, height, numXDivisions, numYDivisions);
DynamicsShape meshShape = DynamicsShape::NewMesh( cloth );
MeshActor clothActor = MeshActor::New( cloth );

Change-Id: I5c89bfd481d6162f8f17e03710c320e8fbb249bf
Signed-off-by: David Steele <david.steele@partner.samsung.com>