mandos-monitor: Use Python's standard loggging module
* mandos-monitor: Use Python's standard loggging module, also for warnings. Suppress BytesWarning from urwid when exiting. (log): New global logger object. This replaces UserInterface log_message(). (MandosClientWidget.__init__): Remove "logger" argument. (MandosClientWidget.using_timer): Wrap self.update_timer using new glib_safely() function. (glib_safely): New function to log any exceptions instead of letting exceptions propagate up to GLib. (UserInterface.__init__): Remove "log_level" argument. Set new "loghandler" attribute, instance of new "UILogHandler". (UserInterface.log_message): Removed. (UserInterface.log_message_raw): Renamed to "add_log_line"; all callers changed. Also fix off-by-one error in max_log_length logic. (UserInterface.run): Add self.loghandler to logger "log". Wrap self.process_input using new glib_safely() function. (UserInterface.stop): Remove self.loghandler from logger "log". (UserInterface.process_input): Make verbosity toggle affect log level of logger "log". (UILogHandler): New.