Serialize RigidCollisionRepresentation

1. Register RigidCollisionRepresentation in the ObjectFactory.

2. Add 'SURGSIM_CLASSNAME'.

3. Serialize member data m_physicsRepresentation.

4. Add UnitTest for RigidCollisionRepresentation.
Simplify headers in RigidCollisionRepresentation

1. Use forward declaration if possible.

2. Remove unused headers.

3. Add header to other .cpp file to make build successful.
Serialize RigidCollisionRepresentation

1. Not serializing RigidRepresentation in a RigidCollisionRepresentation
   since it's a weak_ptr<>.

2. Enable the serialization of a RigidCollisionRepresentation in
   RigidRepresentationBase.

3. Update UnitTests.
Update UnitTest for serialization of FixedReprsentation