Eliminate OVERRIDE_11 and FINAL_11 macros.

Remove the macro definitions from Simbody, and replace `OVERRIDE_11 -> override` and `FINAL_11 -> final` everywhere. We said Simbody 3.6 and above must be compiled with a C++11 compiler. This seals the deal.

**Reviewer question**: is OpenSim still depending on Simbody to define these macros? Should I leave the macros defined unconditionally to `override` and `final` in case anyone is still using them?
SWIG 3.0 and up allow the use of override and final. Also, swig 3.0.2 works with our code (opensim). However, we still currently use 2.0.10.  If we still want to support 2.0.10, this should be:

```cpp
#ifndef SWIG
    #define OVERRIDE_11 override
    #define FINAL_11 final
#else
    #define OVERRIDE_11
    #define FINAL_11
    #undef override
    #define override
    #undef final
    #def final
```

cc/ @aymanhab