STATS: allow the user to change the color of the charts

[elB4RTO]

Introduce some options in the configs section to let the user define the colors to use for the charts

• Warnings:
  • Select the color for non-warning bars
  • Select the color for warning bars

• Speed:
  • Select the 3 colors of the line gradient

• Daytime:
  • Select the color of the bars

• Relational:
  • Select the 3 colors of the area gradient
  • Select the color of the outer line