allow asymmetric mode check plots

In order to close issue #320 the pre-processor would need to be updated, to allow setting the following options in the estimation command

mode_check_symmetric_plots (1 or 0)
mode_check_neighborhood_size (real or inf)

when 

mode_check_neighborhood_size=inf

mode_check.m automatically sets

mode_check_symmetric_plots=0

i.e. we plot the profile of the posterior kernel in the entire prior range

thanks a lot