Exercise: Improve the color selector

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There are several parts of this exercise:

  • The color selector created previously shows menu items numbered from 0. Change it so the displayed numbers will start at 1 but that it will still work correctly.
  • Currently the user can give any value on the command line. Incluing "nonsense". Check that the given value is indeed one of the possible values hard-coded in the script. Report an error and quit if it isn't.
  • Allow the user to supply a flag called --force If this flag is present allow any value as a color. Even "nonsense".
  • Read the names of the valid colors from the colors.txt file.
  • Allow the user to supply a --file flag as in "--file mycolor.txt" and take the name of the file with the colors from there.