chore(library/simplifier): cleanup and add comments
chore(library/simplifier): cleanup and add comments

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

digama0/lean,leodemoura/lean,fgdorais/lean,levnach/lean,dselsam/lean,johoelzl/lean,soonhokong/travis_test,sp3ctum/lean,digama0/lean,sp3ctum/lean,fpvandoorn/lean,htzh/lean,eigengrau/lean,soonhokong/lean-windows,codyroux/lean0.1,UlrikBuchholtz/lean,leodemoura/lean,javra/lean,fpvandoorn/lean,c-cube/lean,rlewis1988/lean,htzh/lean,soonhokong/travis_test,fpvandoorn/lean2,johoelzl/lean,soonhokong/lean,levnach/lean,soonhokong/lean-osx,Kha/lean,Kha/lean,soonhokong/travis_test,fpvandoorn/lean2,javra/lean,digama0/lean,digama0/lean,eigengrau/lean,UlrikBuchholtz/lean,c-cube/lean,c-cube/lean,soonhokong/lean-osx,leanprover-community/lean,leanprover-community/lean,htzh/lean,johoelzl/lean,leanprover/lean,soonhokong/lean,avigad/lean,soonhokong/lean-osx,fgdorais/lean,eigengrau/lean,soonhokong/lean-osx,johoelzl/lean,sp3ctum/lean,avigad/lean,leanprover/lean,codyroux/lean0.1,eigengrau/lean,soonhokong/travis_test,leanprover/lean,javra/lean,sp3ctum/lean,fgdorais/lean,Kha/lean,fpvandoorn/lean2,digama0/lean,avigad/lean,UlrikBuchholtz/lean,levnach/lean,Kha/lean,dselsam/lean,fpvandoorn/lean,codyroux/lean0.1,c-cube/lean,soonhokong/lean-windows,soonhokong/lean-windows,johoelzl/lean,digama0/lean,soonhokong/lean-windows,fpvandoorn/lean,fgdorais/lean,soonhokong/lean,fgdorais/lean,leanprover-community/lean,leodemoura/lean,dselsam/lean,fpvandoorn/lean,codyroux/lean0.1,dselsam/lean,leodemoura/lean,dselsam/lean,htzh/lean,UlrikBuchholtz/lean,dselsam/lean,c-cube/lean,sp3ctum/lean,avigad/lean,rlewis1988/lean,rlewis1988/lean,leanprover/lean,soonhokong/lean,fgdorais/lean,rlewis1988/lean,fpvandoorn/lean2,leodemoura/lean,htzh/lean,rlewis1988/lean,fpvandoorn/lean2,levnach/lean,johoelzl/lean,Kha/lean,soonhokong/lean-osx,rlewis1988/lean,soonhokong/lean-windows,fpvandoorn/lean,leanprover/lean,Kha/lean,leanprover-community/lean,javra/lean,eigengrau/lean,leanprover-community/lean,leanprover-community/lean,soonhokong/lean,javra/lean,levnach/lean,avigad/lean,avigad/lean,leanprover/lean,UlrikBuchholtz/lean,leodemoura/lean