The Union Square Main Streets newsletter announced new tenants would be setting up shop at 11 Bow St. in Somerville. Diesel Cafe has signed a lease to create a cafe on the first floor and renovations have begun this week. This is the second location for the thriving Davis Square business. Upstairs, The Zeitgeist Gallery has leased 1,500 square feet of space to present a wide range of arts programming.The Globe picked up on......