Fix for issue 11: Update support for mseeds with variable record

Fix for issue #11 : The trace scan list will now show some of the header data for mseeds with variable record length (stat:chan:loc:net & endianness), but not the start/end times. The log will also display the message: "WARNING: File size is not an integer number of block size (4096). Start/End times cannot be displayed. To fix variable record length, use fixhdr".