Fix many bugs

1. FIx backspace undo bug
2. Fix cut/paste bug
3. FIx measure area color according to bpm
4. Increase default max_y and max_lines
5. Fix ctrl + arrow action

Cache before Load

Cache current step data to .cache.ucs before load new file

FIx cache and logging

1. Save ucs file to cache.ucs before you quit
2. Make error log file if crahsed

First release

First release