CSVRecord implements get(int) and size() methods so it’s already pretty
much a list.  However, because it does not implement the List interface,
users cannot take advantage of convenience methods such as subList nor
can they pass records around to methods accepting lists.

Make CSVRecord extend AbstractList so that it implements List interface.

Because AbstractList pravides iterator() implementation, this allows us
to delete said method (alongside toList() method) reducing amount of
code.