Separate seasonal and non-seasonal initials

[config-i1]

Possible solutions:

1. Separate initial and initialSeason;
2. Accept a list in initial, so that initial[[1]] is the vector of non-seasonal ones and then [[2]], [[3]] correspond to specific seasonalities. If a seasonal is not provided, it should have NA.

[config-i1]

Additionally, this should also accept initials for ARIMA and maybe xreg as well.

How about a named list:

• initial$nonseasonal
• initial$seasonal[[1]], initial$seasonal[[2]], ...
• initial$ARIMA
• initial$xreg

If vector is provided, the stuff is used one after another.

[config-i1]

An example with the idea with the list: list(level=1000, trend=1, seasonal=list(c(-100,90,-120,135), c(1,2,3,4,5,6,7,8)), ARIMA=c(1,2,3), xreg=c(1,2,3,1,4,24))