Loosen check on length of date value.  Allow anything that is 6+ chars long.
Fix ARI-3289.  Date values are stored in the index unperturbed.  Dates
are indexed by year and year+month as long as they have enough digits.
Fix https://github.com/aaronbinns/jbs/issues/7

Parse input files can come from non-HDFS filesystems if they are given
full-URLs containing the relevant filesystem protocol.