Shares down on Russia sanctions, weak U.S. housing; dollar pauses

* Russia stocks tumble anew after new sanctions * Wall Street falls in early trade on weak housing data; bonds gain * Dollar pauses for breath after strongest week since March (Updates with U.S. market open) By Angela Moon NEW YORK, July 28 (Reuters) - World stock markets fell on Monday as new European sanctions against Moscow chilled the already frosty relationship with Russia while the dollar hovered near six-month highs against a basket of major currencies. U.S. stocks o