provisions for making shock decompositions for epilogue variables.

In case the epilogue formula is non-linear, the non additive non-linear term is distributed proportionally to the size of the individual shock contribution.
It is triggered by new option with_epilogue, applicable to commands:
1) shock_decomposition, realtime_shock_decomposition,
where preprocessor should trigger
options_.shock_decomp.with_epilogue=true;
2) initial_condition_decomposition
where preprocessor should trigger
options_.initial_condition_decomp.with_epilogue=true;