Changes from version 3.0.0 to 4.0.0
 * ETS models a la Hyndman added with same syntax than UC
 * Multiple diagnostic statistics and other useful tools (tests, zplane, etc.)
 * Some tools added to perform slide forecasting (slide and plotSlide)
Changes from version 2.2.3 to 3.0.0
 * Added models: td (trend with fixed slope), linear (seasonal model as in standard BSM)
 * Time-Varying regression terms for input variables
 * Box-Cox lambda automatic identification
 * New inputs trendOptions, seasonalOptions and irregularOptions introduced
 * Some bugs fixed
Changes from version 2.2.2 to 2.2.3
 * minor bugs fixed
Changes from version 2.2.1 to 2.2.2
 * Arma identification deactivated in some weird cases
 * minor bugs fixed
Changes from version 2.2 to 2.2.1
 * Help documentation improved
 * Bugs fixed
Changes from version 2.1.2 to 2.2
 * New function getp0 to get initial conditions of parameters
 * Output table of UCvalidate changed to show parameters and their asymptotic s.e. in the original parameter space
 * Many bugs fixed. Among them the most important are NaNs in covariance of parameters
 * New fields added to UComp objects: covariance matrix of estimates (covp); number of iterations in estimation (iter)
 * Zero components not return to make plot(model) prittier.
 * Labels added to estimated states.
 * Documentation improved.
 * Sales time series removed.
 * Predict function extended to prediction intervals
Changes from version 2.2 to 3.0
 * Random Walk with drift model added
 * Inputs trendOptions, seasonalOptions, irregularOptions added
 * Regression with inputs with time varying parameters
 * Some bugs fixed
 * Wrapper functions simplified