port QRDecompositionHouseholderColumn to HouseholderColQR
add QRDecomposition interface
refactor HouseholderQR
add tests to TestHouseHolderQR
add tests for HouseholderColQR
port LinearSolverQrHouseCol to QRHouseColSolver
fix error
all tests for QRHouseColSolve work
add solveLeastSquares to Linear
pull from develop
minor changes
Merge pull request #56 from prasant94/least_squares

Least squares solver