- additional operators:
  + compound assignment
  + inner product: operator&
  + outer product: operator^

- additional functions:
   - MatrixBlock methods: subColumn, subRow, subMatrix
   - L2 norms for matrix or column
   - trace, diag, round, transpose

- MatrixBlock methods: col(), block() are deprecated since their
  access patterns with (size, offset) are unnatural/unwieldy.

- verifications by test/Matrix/Test-Matrix