ENH: improvements, modernization of matrix containers (#1220)

- add iterators, begin/end, empty() methods for STL behaviour.
  Use standard algorithms where possible
     * std::fill, std::copy
     * std::min_element, std::max_element

- access methods consistent with other OpenFOAM containers:
     * data(), cdata(), uniform()

- Use ListPolicy to impose output line breaks

- Can recover matrix storage for re-use elsewhere.
  For example, to populate values with 2D i-j addressing and later
  release it as flat linear storage.

- added minMax() function for Matrix

- additional inplace +=, -=, *=, /= operations

Matrices are not yet move constructable, pending a use case.