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?
The options seem to be (1) using swig 3.0.2 (this is fine with me, since 3.0.2 is in ubuntu 14.10), or (2) using the macros above.