[DynareDev] Treatment of constant-option

Dear all,

the preprocessor currently allows setting ```constant``` and ```noconstant```-options (although they are not fully documented yet).

But in ```dynare_estimation_init.m``` any such setting is automatically overwritten by:

if all(abs(oo_.steady_state(bayestopt_.mfys))<1e-9) options_.noconstant = 1; else options_.noconstant = 0; end

I don't really see the point of keeping the option. Rather the user should specify a correct observation equation. In that case, the current treatment should assure correct results.

Best,

Johannes