Advanced handling of `loggit` vector inputs

[MEO265]

Vector (and list) inputs (longer than one entry) in loggit() currently lead to a warning and several entries in the log.
Since both JSON and data.frame offer an easy way to save a list or vector per entry, there should be an optional controllable behavior with the options:

• "warn": The previous multiline behavior including a warning. (Should it remain the default behavior?)
• "multiline": The previous multiline behavior without a warning. (Maybe the new default?)
• "toString": Vectors that contain more than one element are tried to be converted into a single string using toString()
• "vector": The elements are all converted using as.character() and entered as a list in the JSON log