improve memory use and bring up to date with current catalyst version.
Update copyright/boilerplate text.
fix spacing
Coding guideline improvements
use core function to get total sitedata use which makes better use of pathtodu
tables defined in file not used in this version.
Save output of Du to config var when used.
tidy up lang and allow config to display empty courses and number of users to display
Tidy up strings, add some more configuration options.