MAHOUT-1566: (Experimental) Regular ALS factorizer with conversion tests, optimizer enhancements and bug fixes.

This closes apache/mahout#6. (Re-commit).

Squashed commit of the following:

commit 32d5183543ee032770bfcebe0a5b2e22b3a388e3
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Wed Jun 4 12:31:57 2014 -0700

    removing commented-out section

commit 8e14bf0cf44a5ee86b0c137e8fbb0a8e75bf6ca8
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Tue Jun 3 13:44:01 2014 -0700

    parameter doc

commit cfa207b1bf98fd941b4d0d48baab4ac35b0deb03
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Tue Jun 3 13:42:12 2014 -0700

    +License on DQR

commit d9249968cd444ab90d92fa5197a5893f32e8c5a8
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Tue Jun 3 11:42:18 2014 -0700

    Adding regularization parameter. Refactoring decompositions and their tests into single package (for both distributed and non-distributed stuff).

commit f8ef52fe33dcf6259156ed913ac86dbad6d1a12f
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Tue Jun 3 11:05:52 2014 -0700

    flipping elementwise operator to OK in-place computation by default (back to where it were). For now. See if the problem surfaces frequent enough to switch to cloned computations.

commit dce371fbdbd17b9c1a3c79260dc8e1180e6073ee
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 2 18:48:33 2014 -0700

    Switching elemnetwise operators to non-inplace execution by default. This will create GC overhead but it is more benign for side effects.

commit c92a6cca9eea1c9d15c5fee9c29c79ef9ed3c77f
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 2 17:53:41 2014 -0700

    Fixing bug. Non-idempotent in-place elementwise computations are still an issue

commit 775490da0f28887350c8725909d4af24e8f37310
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 2 15:17:11 2014 -0700

    WIP; bug in zipping -- does several rounds over partitions causing unidempotant side effects.

commit 565ecb0ca2bb6b1dda30af2c81bdeb1be7fae9fe
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri May 30 18:11:42 2014 -0700

    stopping computation on negative convergence too (i guess in ideal data it converges too fast and rounding errors could push rmse back up.)

commit 2c9ba249e7dc312c2919a60d43e781eae67c51a9
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri May 30 17:50:36 2014 -0700

    license

commit 4b525e5011c002bdb4eb37e27699dc1f89f63d63
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri May 30 17:43:31 2014 -0700

    print out iteration rmses in the test

commit 84949a533270cb2bfe735f85321706a424a950cf
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri May 30 17:36:00 2014 -0700

    Bug fixes, test ok

commit c47995e74dce76e74bc4a58dbd473120da407dc0
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Thu May 29 21:32:23 2014 -0700

    ALS