Remove MATLAB interpolators from examples

There are examples that use MATLAB interpolations that are just second-order and that are not appropriate. They should be replaced by MOLE interpolators which not only are mimetic but they actually are of higher-order. The examples are: burgers1D, convection_diffusion3D, hyperbolic1D, lock_exchange, richards, schrodinger2D, test_grad2DCurv, test_grad3DCurv, test_lap3DCurv, wave2D, wave2D_case2.