MAHOUT-1583: cbind() operator for Scala DRMs
This closes apache/mahout#20

Squashed commit of the following:

commit 1baf3fcebf2cd49eb6487afe4eaed689653a3562
Merge: 41f0671 9bfb767
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 12:32:34 2014 -0700

    Merge branch 'master' into MAHOUT-1583

commit 41f0671c9ccca81883475437fe18056563c1f8ac
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 12:27:26 2014 -0700

    Adding assignment time comparison test

commit 6e115c87639ffb111b2e089d7ecdf0eaeecbb02b
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 16 18:42:42 2014 -0700

    + Licenses.

commit d3e905b5a92735822efe717f8b7a57c80bc56478
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 16 18:09:59 2014 -0700

    initial writeup
MAHOUT-1529: third collection of various edits against private branch

Squashed commit of the following:

commit 4328aae135bc56c02b944c21af2cfd6629b262bf
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 13:13:26 2014 -0700

    Various 1529-related stuff collected from private fork
fixing cross-coocurrence tests
MAHOUT-1529 (d): moving core engine-independent tests logic to math-scala, spark module running them.
Source: dlyubimov/MAHOUT-1529d
This closes apache/mahout#28.

Squashed commit of the following:

commit 8d693b02e474ca1380c0e1cfa262ec4a47afeeae
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 14 13:03:13 2014 -0700

    minor style

commit f568736a35a8c76c6eb70694ce9feee09ff845dc
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 14 12:57:19 2014 -0700

    + license

commit d47e2dca693c147e6978a6c5e1fe42c1ab73ece3
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 14 12:55:36 2014 -0700

    + license

commit 61e6268d261c875781d430ca7861e0b345f485c3
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri Jul 11 11:31:44 2014 -0700

    style

commit c2406654c3fc7326b87848a23933cd4031a2c9a9
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Fri Jul 11 11:27:53 2014 -0700

    Initial test rearrangement. Pushing engine-independent logic to math-scala. Some renames.
NOJIRA: distributed context property must really be public for engine-agnostic consumers
fixed CoocccurrenceAnalysis A'B instead of B'A, and fixed ItemSimilarityDriver to handle asymmetric A, and B input
merge of current master