Security audit

Don't produce stack trace which looks like crash/include file name in
logging stats

Add to above Dean Gaudet's suggestion: make errors look prettier (like tar).

Add new restore option - bring directory to state it was in, say, 5
days ago, etc.

Michael S. Muegel suggestion: "--char-translate source-char
replacement-string" for use between windows/unix conversions, e.g. ':'
to _colon_.  Also distinguish new vs changed update in lvl 5 logging.


Bugs:

Jamie Heilman's race condition