calculate_cci: notes

[thomas-rasmussen]

• Update documentation. It should be more general, not focused around use with Danish data. Mention automatic handing of SKS codes in DK data later in the description.
• Checking the format on the given date variables to ensure they are indeed dates seems a bit too much. This is more likely to cause confusing/fustration than actually helping. Check what happens if the intnx function used to calculate date difference is used with decimal numbers. It should still work without errors, it will just interpret it wrong (as a datetime?) causing incorrect result? It should be on the user to ensure that the input is correct.
• Check/update notes printed in the log with print_notes = y.
• Consider removing "" prefix in variables in output, and instead check that protected variable names are used instead. Maybe it is still a good idea to require no "" variables in input and use the "__" prefix in temporary variable names during macro execution.