[modules/cpu2] use theme palette colors for core load bars
[modules/cpu2] use theme palette colors for core load bars

As discussed in #556.

- added palette red, orange, yellow, green to nord-powerline

- when used with nord-powerline (or any other theme that has these
  palette colors) and cpu2.colored=1, the cpu2 module will use these
  custom colors to display core load graphs; when colors are missing
  from a theme - it will use default colors

tobi-wan-kenobi/bumblebee-status,tobi-wan-kenobi/bumblebee-status