turn the closures out of processInput()
kickstart of implementing bound (visual) mode

- change 'edit-overwrite' mode to 'overwite' mode.
- add mark: '<, '>
- add style for visual bounding
- fix multiply()
- fix emphasis()
- processInput() does not refer to closures now
- add bound mode mapping
- toggleCase() now uses String#toLowerCase()/toUpperCase()