What started off as a way to get out of summer camp has turned into a labor of love for a Cambridge 10-year-old who passes out over 50 homemade lunches a week to homeless individuals living on the streets near his Central Square home. Little notes of encouragement -- “Have a nice day” or “Try to smile” -- accompany the brown paper bags hand-packed with any variation of peanut butter and jelly, ham and cheese, apples, oranges and potato chips. Liam Hannon, an incoming fifth-gr