Various bugfixes related to filtering and smoothing

- fix length of forecasts in Bayesian estimation and make them consistent across all options
- fix length of classical filtered variables and make them consistent across all options
- Harmonize length of filtered variables coming from calibrated smoother
- makes sure all posterior moments are returned as column vectors
- fixes computation of Smoothed Measurement Errors in Bayesian estimation 
- filters out incompatibility of selected_variables_only option and classical forecasts