Now that Somerville’s Davis Square has been acknowledged as one of the newer hip places for younger bohemian types to look for rentals and for slightly older, wealthier folks to house hunt, it’s no surprise to find a new Indian restaurant opening its doors for business there. There’s nothing unusual about the menu at Diva, which features the usual cast of curries, tandoori oven specials, nan and poori breads and chutney dips. What distinguishes Diva is the decidedly upscale, bistro-style décor, which may have you expecting to pay a few more dollars for dinner than you’ll have to.