Write log file in UTF-8 to fix encoding errors

Some log messages use characters in the Unicode character set that
aren't typically represented in the older encodings. One such example
was  the messages that happen when renaming an item and saving the
project.

Positive note though: errors while logging might not end up in the log
file when the log file is the cause, but they still showed on the
terminal with excessive detail. Also, despite the exceptions and errors,
the project I was testing successfully completed its saving procedures
as a subsequent reload showed. I am personally quite happy with the
degree of thought and care put into the Python logging system. :-)

manuskript/logging.py

@@ -59,7 +59,7 @@ def logToFile(file_level=logging.DEBUG, logfile=None):
     # log files may not be in our users best interest for the time
     # being. (Unfortunately.)
     try:
-        fh = logging.FileHandler(logfile, mode='w')
+        fh = logging.FileHandler(logfile, mode='w', encoding='utf-8')
         fh.setLevel(file_level)
         fh.setFormatter(logging.Formatter(LOGFORMAT_FILE))