High quality resampler

Think of this as rough draft. Taking suggestions to make it robust, error free, and prettier!

For more information:
https://docs.google.com/document/d/1tBEgsJh7QiwNwepXI0eobfK3U8LkJButSyeuFt1degM/edit?usp=sharing

removed: SSE includes

added: 16bit -> float -> 16bit functions
added: linear interpolator and high-quality interpolator functions (including Resampler class)
added: dithering

changed: renamed variables and reformatted a few things to fit with style guide
changed: use s16, u16, s32, u32 etc
changed: store samples and do all computations as floats
changed: volume from 0 - 255
Class functions are only implicitly inline if the implementation is inside the class definition.  That said, it's a bad idea to mark a member function "inline" if the implementation isn't in the header; it can cause linker errors.