QUETTA, Pakistan (Reuters) - Pakistan has detained 30 people in connection with an attack this week on minority Muslim Shi'ites in the southwestern city of Quetta, which killed 44 people and wounded at least 150, police said on Sunday. Police also registered a complaint by relatives of the slain Shi'ites against seven local members of an outlawed Sunni militant group whom they blamed them for the attack. A senior police official, who asked not to be named, told Reuters 30 people had been arrested so far in an extensive investigation into the massacre on Tuesday, when Shi'ites were observing Ashura,...