MAHOUT-1148 - Re-implemented QR decomposition.  On a 60x60 random matrix it is about 8x faster now after the JIT warms up (takes 100 or so decompositions).

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1442428 13f79535-47bb-0310-9956-ffa450edef68