Added new irclogs.py script to process mantisbot's logs

Details in wiki
http://www.mantisbt.org/wiki/doku.php/mantisbt:irc_logs
irclogs.py: improved logging including start+end with timestamp
irclogs.py: use subprocess instead of os.system

Added error handling and logging.
irclogs.py: don't exclude index.php from rsync

Maintenance is easier if the redirection pages and symbolic links are on
the source rather than the target.
irclogs.py: follow PEP8 coding guidelines
irclogs.py: generate redirection page

Backwards-compatibility for links saved before change of dir structure