Hackathon justin

This is pull request for work started on Hackathon, mainly improving Model class with new coding convention of ModelComponent (e.g. replacing the old property style with the new property style). This also deals with a bunch of issues: #95, #99, #100, #101, #102.
Is this reasonable? Seems likely to cause leaks. Would it be OK just to define setIntegrator() to take over ownership of the passed-in Integrator? It would be nice if this allowed getting rid of the _ownsIntegrator flag; those things have been a notorious source of leaks in OpenSim since it is very difficult to get them set correctly.