Completed the overloaded subsref method. Give access to the Time member, which is an object instantiated by @dynTime/dynTime.

Completed the overloaded subsref method. Access to the time member using a syntax like x(1:3) or x(:).

- no longer use the 'noclearall' option when calling Dynare
- test the simulation path for the various stack_solve_algo options
- simplify code

solution implemented consists of adding one extra observation in the presample
used to compute the prior; as a consequence, the numerical results for all
estimations will be slightly different in future releases (thanks to Marek
Jarociński for spotting this)

Added matlab routine to iterate on the state equation approximated at order 2 (needed for nonlinear filters).