make VectorMatrixMN non-final
Implement SparseRowMatrix and SparseColumnMatrix
copyColumnTo for SparseColumnMatrix
more SparseColumnMatrix code
refactoring
more SparseColumnMatrix overrides
extra validation
extra sparse matrix construction function
extra SparseRowMatrix constructor and tests
optimised innerProduct for SparseRowMatrix
transposeInnerProduct for SparseColumnMatrix
misc edits
tidy
BitVector isZero
BitVector magnitudeSquared
fast BitVector dotProduct
BitVector tests