cleaned code that is useless since we transform leads and lags on
period > 1

Ref. manual: list in a single place the MATLAB toolboxes and Octave-Forge packages from which Dynare can benefit

Closes: #224

is contradictory with diffuse_filter or unit_root_variables
declaration. Models with non-stationary variables, but only stationary
observed variables need diffuse_filter option and make a useless call
to kalman_filter_d (this seems better than trying to distinguish these
rare cases)

are not strictly positive.

'steps' values)

Restore the path and add an extra clear all between tests

Do not show plots of the smoothed variables, shocks and errors if nograph option is used. Note that with this option the plot are done behind the scene and saved in fig, eps and pdf format (see trac#216).