Somerville’s housing wars have a new battlefield: a city ordinance that controls conversions of apartments to condominiums, which tenant advocates say has been exploited by landlords, while developers complain it is overly restrictive and possibly illegal.  The fight is playing out in City Hall, where Somerville aldermen acknowledge the 32-year-old ordinance, a vestige of the rent control era, is antiquated and in need of rewriting.  And now a legal challenge is threatening to kill the ordinance outright.   Read the article…………