Add option to set background and text color on a module basis

[nicholas-eden]

Resolves the feature request in issue #307 .

Each mod can use a colors namespace to set the background and text properties, as which will default to the global value if not set.

wtf:
  colors:
    text: "gray"
    border:
      focusable: darkslateblue
      focused: orange
      normal: gray
  grid:
    columns: [40, 40]
    rows: [13, 13, 4]
  refreshInterval: 1
  mods:
    clocks:
      colors:
        background: "darkred"
        rows:
          even: "lightblue"
          odd: "white"
      enabled: true
      ...
    security:
      colors:
        text: "yellow"
      enabled: true
      ...

]

[senorprogrammer]

Thanks!