Solver was inherited from Aliaser
Added multiRun to SolverBenchmark
reworked SolverBenchmark.addSolver:
  now it has 1 agrument and
  uses Solver.alias() as the name of the solver
added ltr/optimization/population_info/population_info_unittest.cc
updated cmake/utests.cmake

Change-Id: Iefc2cc0d0f22a173887967838d14b23b5bb74e08