MAHOUT-1596: implement rbind() operator

This closes apache/mahout#30

Conflicts:
	math-scala/src/test/scala/org/apache/mahout/math/drm/RLikeDrmOpsSuiteBase.scala
MAHOUT-1500: Implement H2O backend for Mahout Scala DSL

Barebone only, no logic yet. Compiles, tests fail with NotImplementedError

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Implement non-operator parts of H2O bindings

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Implement non Linear Algebra ops in H2O backend

i.e, mapBlock() and rowRange()

Provide dummy methods for all operators

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Implement Linear Algebra ops in H2O backend

- A'
- A'A
- A'B
- AB'
- A (element-wise) B
- A (element-wise) Scalar
- AinCoreB
- Ax
- Atx

All MathSuite tests are passing.

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Add String key support to DRM

Strings are stored in a Vec along with Frame in CheckpointedDrm

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Implement Par() operator

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Implement Cbind() operator

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: use accessor methods instead of direct field access

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: mahout h2o-node CLI for aux worker processes

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: refactor frame_from_matrix() to reuse empty_frame()

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: SequenceFile persistence (read/write) support

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Add tests for distributed operations

Mostly copy tests from sparkbindings with minor/trivial changes

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: add README

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: cleanup

- add code comments
- style fixes
- minor cleanups

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: use the new test suites
MAHOUT-1500: make context public in CheckpointedDrmH2O

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Remove MathSuite from h2o/src/test

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: ValueString API changes

Signed-off-by: Anand Avati <avati@redhat.com>
MAHOUT-1500: Simplify empty_frame()

Signed-off-by: Anand Avati <avati@redhat.com>