feat(library/tactic): expose COND and WHEN tacticals in Lua, add HOL-like tactical names
feat(library/tactic): expose COND and WHEN tacticals in Lua, add HOL-like tactical names

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

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