Index numbers are in terms of the order in kbase. UTF-8 codepoints are
usually of class "hexmode", but character strings starting
with "0x" or "0X" are also accepted in the key.
For output = "kanjivec", the GitHub package kanjistat.data has to be available or
an error is returned. For output = "all", component kanjivec is set to NA if
kanjistat.data is not available.