New folder colors

[ironjan]

• after many years, there are new folder backs
• Much color, much awe.
• But Colors missing in tool.
• They should be added.
  • (green | white | yellow | red | blue) on black.

Places in code:

• https://github.com/ironjan/klausurtool-ror/blob/master/config/locales/de.yml
• https://github.com/ironjan/klausurtool-ror/blob/master/app/models/old_folder.rb
• https://github.com/ironjan/klausurtool-ror/blob/master/config/locales/de.yml

Open queestions:

• Can colors be moved to a config-file or so? Would make things more maintainable.