Pulling LocalGemm and friends out of the internal namespace and merging HPDInverse with Inverse, HPDDeterminant with Determinant, SolveAfterCholesky with Cholesky, and SolveAfterLU with LU

--HG--
rename : include/elemental/lapack-like/SolveAfterCholesky.hpp => include/elemental/lapack-like/Cholesky/SolveAfter.hpp
rename : include/elemental/lapack-like/HPDDeterminant.hpp => include/elemental/lapack-like/Determinant/Cholesky.hpp
rename : include/elemental/lapack-like/CholeskySolve.hpp => include/elemental/lapack-like/HPDSolve.hpp
rename : include/elemental/lapack-like/HPDInverse/LVar2.hpp => include/elemental/lapack-like/Inverse/CholeskyLVar2.hpp
rename : include/elemental/lapack-like/HPDInverse/UVar2.hpp => include/elemental/lapack-like/Inverse/CholeskyUVar2.hpp
rename : include/elemental/lapack-like/SolveAfterLU.hpp => include/elemental/lapack-like/LU/SolveAfter.hpp
Renaming HouseholderSolve to LeastSquares and adding documentation for the Kahan matrix

--HG--
rename : examples/lapack-like/HouseholderSolve.cpp => examples/lapack-like/LeastSquares.cpp
rename : include/elemental/lapack-like/HouseholderSolve.hpp => include/elemental/lapack-like/LeastSquares.hpp
More steps towards removing the elem::internal namespace

--HG--
rename : include/elemental/lapack-like/Bidiag/UnblockedL.hpp => include/elemental/lapack-like/Bidiag/LUnb.hpp
rename : include/elemental/lapack-like/Bidiag/UnblockedU.hpp => include/elemental/lapack-like/Bidiag/UUnb.hpp
Fixing subtle issues arising in HermitianUniformSpectrum and NormalUniformSpectrum due to switch from PLCG to simple in-house random number generation.
Merged with Jack's upstream changes