Multiple entries in various #Attributes

[marwin89]

Suggestion:

• Implement multiple entries in #GENRE, #CREATOR, #EDITION, #LANGUAGE, #TAGS
• separated with comma ","

(according to official common Song format Specification v1.1.0 - release on: 1th Dec 2023)

[flokuep]

Editions, Genres and Langauges are already multi-value fields, but interpreted in a different way (multiple tags of the same type are allowed). The main complexity here is to not break the old behaviour and add a feature switch for the new behaviour.

• Adjust creator in the Song-class so that it's also a multi-value field.
• Add RawEdition, RawLanguage etc. to the Song class to keep the original values
• After reading all tags, check the version-tag of the file. If it is > 1.1.0, split the RawValues by comma and add them to the according fileds.

Complexity: S