MAHOUT-1508: Performance problems with sparse matrices

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1586851 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1420: Add solr-recommender to examples

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1586920 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1420: Add solr-recommender to examples; typo fix

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1586921 13f79535-47bb-0310-9956-ffa450edef68
Initial commit for parallel sgd factorization.