Make PosteriorIRF obey irf_shocks

The matrices are still initialized to have the size M_.exo_nbr, but the computations (e.g. moments) are now only performed for the shocks in irf_shocks. PosteriorIRF_core2 still does not allow for a selection, but the check for IRFs>10^(-6) already effectively prevents the plotting.
Make unconditional forecasts save figures to graph folder

Also provides more expressive title
Use ilu with type=ilutp instead of nofill

Contrary to luinc command ilu with nofill option doesn't not allow for partial
pivoting
Remove spurious displayed variables
Fix nonexistent variable names
Fix incorrect reporting of failed test number
Fix mangling of lasterror() under Octave
Disable test with block and stack_solve_algo=3 under Octave (Ref #407)
Merge pull request #405 from JohannesPfeifer/cond_forecast_graphs

Make unconditional forecasts save figures to graph folder
Merge pull request #403 from JohannesPfeifer/irf_shocks

Make PosteriorIRF obey irf_shocks
Make BVAR obey graph-options and save to graph folder
Merge pull request #404 from JohannesPfeifer/BVAR_graphs

Make BVAR obey graph-options and save to graph folder
Merge pull request #408 from rattoma/master

allow asymmetric mode check plots
Add mode_check_{neighbourhood_size,symmetric_plots} in preprocessor and manual

Closes #320
Add missing graph title that lead to crash
Merge pull request #411 from JohannesPfeifer/cond_forecast_graphs

Add missing graph title that lead to crash in unconditional forecast test