Add MSSMD5O: MSSM including dimension-5 operator
Do not constrain Yv and Mv in MSSMRHN model file

They shall be determined by the matching class in the tower example.
Replace MSSM by MSSMD5O in tower example

In the lower model, the low-energy neutrino masses and mixing determine
WOp, the coefficient matrix of the dimension-5 operator.  At the
matching scale, the seesaw relation is used to fix Yv and Mv in the
upper model from WOp plus supplementary conditions on the structure of
Yv.
src/linalg2.hpp: hide function objects in functions

to avoid name collisions.
src/linalg2.hpp: rewrite documentation in doxygen format