[SYSTEMDS-3695] Fix frame builtin nary append for Spark backend

[e-strauss]

This patch implements the nary append operation for frames (cbind and rbind). For the cbind, there are two physical implementation:

• map-size cbind (w/ broadcast)
• reduce-size cbind
  I added test cases to check the functionality of the n-ary operators and I also enabled the Word-Error-Rate test case.

Additionally, this patch fixes the map-size cbind operation to handle misaligned frameblocks.
As discussed, I will make another PR for the misalignment fix of the other physical operator

[mboehm7]

LGTM - thanks for the patch @e-strauss. During the merge I only fixes minor warnings and formatting issues.