Add unique errors for every FKO_ERROR_INVALID_DATA.  Needed this to
track down mystery errors (#98).
minor ChangeLog update for --stanza-list
Merge remote-tracking branch 'hlein/unique_errors'

[libfko] (Hank Leininger) Contributed a patch to greatly extend libfko
error code descriptions at various places in order to give much better
information on what certain error conditions mean.  Closes #98.
ChangeLog/CREDITS update for Hank's libfko error code patch