Add accuracy class
Add PreprocessSegmentHitRatio data extractor for accuracy class use
Add preloader to provide assertion and preload modules ability
Add scoped_frames() v2
Add new version of diff_next in pre/probe

For simplicity, removed multi-process support from `prepare`.
Improve usability of diff_next, and probe.
Also rewrite scoped_frames() in `video` to `frame_set()`.
Adjust diff_next frame_id alignment result.
update readme
Improve reducer probing usage
Add exp/pre preprocess constants

Move constant array in lib/exp/evaluator/accuracy_data_extractor, lib/plotter/pre/base
to lib/exp/pre/__init__
Make `probe.diff_next` much like previous version

Also fix bugs in `video`
PrePlotter improvements

Add accuracy plotter
Add @render_base
Use self.`key` in `exts`
Add plot_filer to save plot result
Using 'eps' as default format
Improve batch_frame_ratio result

use Const.Doffset in lib.exp.pre to get better frame ratio
Improve roc_curve rate
Add transparent legend
Refactor fc_shr_cp_comparisons to fc_cov_comparisons
Add count values to fc_cov_comparisons
Add frames plot
Improve frames_plot
Add ax_helper
Add delay_plot, refactor Const zipkeys