write_latex_definitions: remove lines that prevented this code from being included in a larger latex doc

Closes #549

Fixes to mode_compute=5. (1) force univariate steps at every iteration: ...

Fixes to mode_compute=5. (1) force univariate steps at every iteration: improve robustness at the expenses of a bit less efficiency; (2) fix gradient computation for special cases when the value of the parameters get stacked at the prior boundary.

Trap the case where only one parameter is estimated and only one non-con...

Harmonize plotting of IRFS

Similar problem to #446

Trap the case where only one parameter is estimated and only one non-constant row is available in Jacobian: (1) do not use vnorm; (2) do not use advanced option.
(cherry picked from commit d9856879)

In stoch_simul.m IRFs were only printed if they were not flat instead of checking whether the IRF is different from 0. Unit root responses were thus filtered out, e.g. C=0.2 for all t was not displayed.

Document treatment of parameters in steady state files

Changed documented behaviour of @dseries/save method (do not document the default value of basename).

Continue harmonizing figure titles in GSA