linear solver<fullMatrix> : avoid copy and allocation

Geo/GFaceCompound.cpp

Mesh/BackgroundMesh.cpp

Mesh/highOrderSmoother.cpp

Numeric/fullMatrix.h

Plugin/Distance.cpp

Solver/dofManager.h

Solver/elasticitySolver.cpp

Solver/linearSystem.h

Solver/linearSystemCSR.cpp

Solver/linearSystemCSR.h

Solver/linearSystemFull.h

Solver/linearSystemGMM.h

Solver/linearSystemPETSc.cpp

Solver/linearSystemPETSc.h

Solver/multiscaleLaplace.cpp