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
Allow asymmetric mode check  plots, using the new option

mode_check_symmetric_plots (=1 at default, i.e. current behaviour)
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
Check in McMCDiagnostics.m whether all consecutive MH files are present

Closes #390
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
Bug fix for negative values of x(kk)
Merge pull request #413 from rattoma/master

bug fix mode_chek
Merge pull request #401 from JohannesPfeifer/MCMCdiagnostics

Check in McMCDiagnostics.m whether all consecutive MH files are present
Add interface and doc to use_univariate_filters_if_singularity_is_detected option

Closes #414
Revert "Reset oo_.{exo_}steady_state to zero before endval"

This reverts commit cf146ec4e50b83bb17f6890b936d8d89e7ef6664.
Fix doc for uninialized values in endval block
Fix wording
Fix bug introduced in 767dce0a