remove legacy solver examples

utils/solvers/legacy/c++/solver.cpp

utils/solvers/legacy/c++/solver.opt

utils/solvers/legacy/c/GmshClient.c

utils/solvers/legacy/c/GmshClient.h

utils/solvers/legacy/c/solver.c

utils/solvers/legacy/c/solver.opt

utils/solvers/legacy/perl/GMSH_CLIENT.pm

utils/solvers/legacy/perl/solver.opt

utils/solvers/legacy/perl/solver.pl

utils/solvers/legacy/python/Gmsh.py

utils/solvers/legacy/python/postcsv.opt

utils/solvers/legacy/python/postcsv.py

utils/solvers/legacy/python/testcsv.csv

utils/solvers/legacy/python/testcsv.geo

utils/solvers/legacy/python/testcsv.msh