mode2: smoother move

- improved conditions
fixedsidebartop <- fixedsidebartop - sidebarmargintop - sidebarmarginbottom

- to simplify it
Scroll mode option added, a bug fixed

- option menu for scroll mode ('Quick Reverse Mode')
- the bug of 1st time option save error has been fixed
format code with PhpStrom

- only space changes
smoother switch back

- adjust details