The Mark Morris Dance Group turns 25 this year, and the company is humming along on all cylinders, its schedule crammed full and its continued artistic relevance continually extolled. “There is also a settled-in sense of comfort — dare one say domesticity? — for this once shaggy-maned provocateur who seemed to cultivate a personal image of outrageousness, even as his early dances resonated with an earthy honesty that suggested a kinship with an earlier, more forthright era of modern dance.”