#log
  closes current log-file
#log <filename> [append|overwrite|html]
  starts logging all data from main window to the file
  if mode is not specified then default settings from Options
  is used
#log <filename> all|<nlines> [append|overwrite|html]
  starts logging and writes to the beginning of logfile
  last <nlines> lines for scrollbuffer or all available lines
  works also with RMA/HTMLTimestamps