There is a breed of performance, usually a solo show, that is not about presenting a choreography or a text. It’s more like: “I want to give you something, I’m not sure what form it’s going to take, I just want to be with you and I want you to see me.” If that sounds a little solipsistic, it really isn’t. At least not in Katherina Radeva’s 40/40, an exercise in generosity of spirit.