Jennifer L. Nelson has a way with characters. They can be silly, then suddenly turn profound; they can be serious, then act totally bizarre. And those characters have a way with words. One of Nelson’s greatest gift is her ability to create entertaining dialogue, as she has in “24, 7, 365” at the Atlas Performing Arts Center. “24, 7, 365” is a multilayered comedy that begins with what seems to be a lighthearted discussion of what happiness is and what life would be like if we could have it all the time.