Add M × N matrix : vector addition support

[chrissimpkins]

Requirements:

• matrix and vector column and row lengths must be the same

Properties:

commutative (A + B = B + A)
associative ((A + B) + C = A + (B + C))
additive identity with zero matrix (A + 0)
additive inverse (A + -A)

Questions:

• how do we approach the Vector shape? Always a column vector?