Added native CPU optimization options to CMake

This PR gives the user the option to enable native CPU compiler optimizations.

The two added options are:
- `USE_NATIVE_OPTIMISATIONS`: adds the `-march=native` compiler flag on GCC-like compilers. Tells the compiler to use all of the host CPU's available instruction set and extensions for maximum performance.
- `USE_SSE_OPTIMISATIONS`: tells the compiler to use SSE instructions when available. (SSE2 on MSVC, SSE3 on GCC. MSVC does not support SSE3)

The two options are turned off by default.