[added] chance for yellow named loot to drop with slightly higher stats
[changed] restructured legendary and exceptional chance to check
legendary first, then exceptional, then yellow

Change-Id: If88ab4131d7ce65070fb07c8943189190716829c
[fixed] mantis #4289

Change-Id: I8a0d96a0453c458ebc3a194b54da1c108d66f0bc
Merge "[added] chance for yellow named loot to drop with slightly higher stats [changed] restructured legendary and exceptional chance to check legendary first, then exceptional, then yellow" into unstable