Build System cleanup and fixes

This pull request fixes the following issues:

* Now builds again using MSVC
* MSVC and regular Makefile now generated via cmake as follows:

```
cmake .
make
```

* horizonatlbitpacking.cpp now in correct name space 
* Automatic SSE4 / AVX / AVX2 detection via cmake
* Fixed various compiler warnings under MSVC and gcc-4.9