Wrong datestring written to the header of the metadata-1.arc

ARC-header made by Heritrix:
filedesc://2-2-20070523131223-00000-mette.kb.dk.arc.open 0.0.0.0 20070523131223
text/plain 1277
ARC-header made when creating the metadata-1.arc file:
filedesc://2-metadata-1.arc 0.0.0.0 null text/plain 77
So we write "null" where Heritrix write "2007052313122" as datestring
We have until now assumed in ARCUtils.createARCWriter(arcFile)
that null given as timestamp in ARCWriter constructor resulted in current time.
But this seems no longer to be the case: Instead a 14digitdateString is required
(according to the javadoc
http://kb-prod-udv-001.kb.dk/heritrix/heritrix-1.12.1/docs/apidocs/org/archive/io/arc/ARCWriter.html
)
Fix: use ArchiveUtils.get14DigitDate(System.currentTimeMillis()) instead of null
for the timestamp
Estimated time to fix: 0.1 MD (needs unittest as well)
NOTE: This bug is originally from Bugzilla bug_id=987.