Aaron Foster never imagined the best way to manage his depression, anxiety and grief would be telling jokes about it, but his solo stand-up show, “Mostly Jokes,” that one reviewer called “subversively hilarious, laugh out loud gallows humor” has helped him, and others, find light in very dark places. Foster quit his job at 50 to become a stand-up comedian and three years later “Mostly Jokes” is a darkly funny look at his strained relationship with his bipolar father, his stra