add ignore_smoothing

[khanghugo]

Needs HLTAS/hltas#11 merged

I try my best not to touch any thing else beside bxt-rs for the implementation. There are a few problems. The obvious one would be how to ignore some frames. Thus a parameter for smoothed_views instead of another member for Frame struct. The upside would be no need to store extra data and doing state stuffs between bxt-rs and BXT. It might look ugly, I guess.

Also, while working on this, unwrap_angles is doing some fractional math with f32. It does have some problems toward what I want to do here. I want to get the input views but after some math the value is a bit off (for examples, -2pi becomes 0.005 degrees). It only affects the output views for the override line, doesn't affect TAS playback so that should be fine.