Refactoring MXNet scala code to use "org.apache.mxnet"

[Roshani Nagmote]

Hello all,

I am working on publishing mxnet-scala release to maven repository and as a
part of that, I will also be refactoring mxnet-scala code/tests/example and
docs to use "org.apache.mxnet" instead of "ml.dmlc.mxnet".

Currently, MXNet-Scala
<http://mxnet.incubator.apache.org/api/scala/index.html> library uses
"ml.dmlc.mxnet" packages. This work will change the way to import modules
when using mxnet-scala package.

*Old way:*

scala> import ml.dmlc.mxnet._
   import ml.dmlc.mxnet._scala> val arr = NDArray.ones(2, 3)
   arr: ml.dmlc.mxnet.NDArray = ml.dmlc.mxnet.NDArray@f5e74790

*New way:*

scala> import org.apache.mxnet._
   import org.apache.mxnet._
scala> val arr = NDArray.ones(2, 3)
   arr: org.apache.mxnet.NDArray = org.apache.mxnet.NDArray@f5e74790


Please let me know if anyone has any thoughts or issues with this change.

Thanks,
Roshani