wdat5: Ignore irrelevant .wlk files (fixes #1)

WDAT5 files should be named YYYY-MM.wlk; however, if the user has
created copies of files, these will have different file names, such as
"Copy of 2011-01.wlk". These are now ignored by loggertodb.
cliapp: Fix writing of "Finished" log message (fixes #2)

When everything was OK, it was failing to write the "Finished" message
to the log file (for loglevel=INFO). This is fixed.