Add our color palette

[Plebysnacc]

Currently we use red-hues similar to the fachschafts-colorpalette.

We should design and implement our actual palette

[dheidemann]

currently figuring out a good way to store system-wide settings. So in terms of implementing the palette, please plan with using the settings query and addSetting mutation respectively. This will look like

mutation addSetting(setting: {
  key: "primary-color"
  value: "#FFFFFF"
  type: COLOR
})

[dheidemann]

settings model is fully implemented now and per default serves a setting with key "primary-color" holding our fs red. See #71 for ref