add real cmdline option handling w/getopt

Besides debug/verbose flags, this allows specifying the config file
on the command line.  Importantly, this lets you do things like
invoke the script with two different config files from crontab,
without requiring two copies of the script!
add -r option and sample configurations

Implement the '-r N' option to use the Nth most recent local snapshot
instead of the newest.  This is useful for avoiding short-lived (e.g.
hourly) snapshots during a long-running backup, e.g. if the backup
hasn't run for a while.

Also add some sample configuration files, for normal and catchup use.
bump version; nuke trailing whitespace