Add dwm_backlight that displays the value of
xbacklight rounded to the nearest int.

- Individual functions no longer contain the square brackets to act as
seperators. These are instead included in the xsetroot command within
dwm_bar.sh itself so that they can be modified much more easily if the user desires.
- Fixed dwm_battery.sh showing a space between the level and '%' symbol
when discharging.
- Added dwm_ccurse to dwm_bar.sh. Guess I forgot that.