Log output fix / enhancement:

When importing QWK messages (e.g. from a QWKnet packet), the statistics logged:
  "Imported n QWK msgs in x seconds (y msgs/sec)"
would logged for all but the last conference (sub-board) being imported into.
Log the import statistics at the end of the import process if a sub-board is
currently open and messages were imported.
Also, log a message when importing QWK netmail.
Thanks to Mark Lewis' eagle-eye, noticing the total messages imported didn't
match all the stats log messages total.