#296 ooDialog reference 4.2.4 ComboBox class missing set/get/remove itemdata methods

[Jon Wolfers]

Mark Miesfeld enhanced ooDialog in v4.2.4 but died with the work incomplete.

He added three methods to the comboBox class
* getItemData
* removeItemData
* setItemData

These need documenting. Their functionality is like that of the similar methods in the listView class, but without reference to sorting.

I will provide that documentation

[Jon Wolfers]

updated and committed combobox.xml

[Jon Wolfers]

I have added these three methods to the ooDialog reference