Introducing Map for error columns and their values

[benedeki]

• Relatively big overwrite to use map instead of errCol and sequence of raw values
• ErrorMessageSubmitJustErrorValue class created to offer the ability to submit errors without source column but with error value
• Some other changes to improve the code

After the presentation, discussions with others and more thoughts, I came to the idea to combine the errCol (which would be better as sequence anyway) and rawValues into one column of map data type. That resulted in a need to do some more exercise in the supporting types, but I believe to for the better.

Also some general code improvements were added as I stumbled upon stuff during the refactoring.

[benedeki]

Moving the the main PR, general direction approved in direct discussions.