feat(frontends/lean/parser): allow 'assume'/'take'/'fun' as notation for apply tactic
feat(frontends/lean/parser): allow 'assume'/'take'/'fun' as notation for apply tactic

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

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