add partial deep merge cache
add more commentary
remove old knockout merge exception

chef 11 has raised an exception on this for nearly 2 years, we
now simply no longer care and don't spend the cycles to check.
provider resolver perf improvement

move the sorting of the providers to after we make the first cut, still
keeps deterministic ordering, but avoids sorting providers we are just
going to throw away.
remove invalid invalidsubtractivemerge specs
remove InvalidSubtractiveMerge class
role_merge can be elmianted now
 #role_merge becomes #merge not #deep_merge
deleted the last end accidentally
WIP: immutabilizing deep merge
Merge pull request #2462 from opscode/lcg/remove-knockout-merge

remove old knockout merge exception