Resolve "Work on const / non-const in wolf base classes"

Closes #184 (closed)

demos/hello_wolf/hello_wolf.cpp

@@ -253,11 +253,11 @@ int main()
     // GET COVARIANCES of all states
     WOLF_TRACE("======== COVARIANCES OF SOLVED PROBLEM =======")
     ceres->computeCovariances(SolverManager::CovarianceBlocksToBeComputed::ALL_MARGINALS);
-    for (auto& kf : *problem->getTrajectory())
+    for (auto& kf_pair : problem->getTrajectory()->getFrameMap())
     {
         Eigen::MatrixXd cov;
-        kf->getCovariance(cov);
-        WOLF_TRACE("KF", kf->id(), "_cov = \n", cov);
+        kf_pair.second->getCovariance(cov);
+        WOLF_TRACE("KF", kf_pair.second->id(), "_cov = \n", cov);
     }
     for (auto& lmk : problem->getMap()->getLandmarkList())
     {