Taskes a list of item parameter matricies and returns a data frame containing delta dots. This is mostly an internal function used, for example to plot items on Wright Maps.
itemListToDeltaDots(myItems)
Returns
A data frame including 4 columns:
id, an integer index reflecting which item this is, in the same order as myItems
itemid, a string with the names from the items in myItems (NA if item list is not named)