Correct bug #262 in treasure hunts loot tier

Make treasure hunt chest loot tier automatically scale to _maxtier
- Final chest always _maxtier, intermediates on scale 0-(_maxtier-1)
- Remove 'multiplier' config option from default.cfg and cfg.py as this
is no longer required or used
- Add some additional debug output in treasure hunt add chest code to
show loot tier calculation
CHANGELOG.txt update