feature/version adds emane version preprocessor support

This feature branch adds emane version preprocessor support to allow plugin source to more easily support multiple emulator versions.

```C++
#if(EMANE_VERSION_CODE >= EMANE_VERSION(0,9,1))
      // code that is specific to 0.9.1 or greater
#endif
```

emane/include/emane/version.h is automatically generated using configure.ac.