some improvement

[AQLT]

• print corrections
• vcov correction and component parameter
• proc_data() to improve export of RegressionItems objects. For example:

  library(RJDemetra)
  jsa <- jx13(ipi_c_eu[,"FR"])
  get_indicators(jsa, 
             "preprocessing.model.out(1)", 
             "preprocessing.model.td(1)",
             "preprocessing.model.lp")
  #> $`preprocessing.model.out(1)`
  #>              Estimate Std. Error    T-stat Pr(>|t|)
  #> TC (4-2020) -35.59245   2.173301 -16.37714        0
  #> 
  #> $`preprocessing.model.td(1)`
  #>         Estimate Std. Error   T-stat   Pr(>|t|)
  #> Monday 0.5593194  0.2280063 2.453088 0.01466076
  #> 
  #> $preprocessing.model.lp
  #>           Estimate Std. Error   T-stat    Pr(>|t|)
  #> Leap year 2.154027  0.7052674 3.054199 0.002433191