DMat and SMat no longer refer to the type "Ring".  Part of DMat refactor

This is instead in the MutableMat class.
Removed get_CoeffRing in favor of ring(), in DMat, SMat.
Moved elementary dmat row+col ops to MatElementaryOps.

This class also has insert/deleter rows/columns.
Forgot to commit MatElementaryOps.hpp.  Also Added MatArithmetic.hpp
moved lapack matrix creation routines to lapack.cpp

removed them from dmat.  Other minors changes.
small changes getting ready for removal of DenseMatrixDef
bug fix in setSubmatrix