Fix XWPFTable row cannot insert to the last position of table

[GGJason]

Fix XWPFTable row cannot insert to the last position of table.
The problem is in CT_Tbl.GetItems1Index method.
Because pos can never be equal to p in for loop, I add a statement to check if the index is -1 and pos == p after for loop. It means that the position is the end of the list.

for (int i = 0; i < items1ElementNameField.Count; i++)
{
    if (items1ElementNameField[i] == type)
    {
        if (pos == p)
        {
            //return itemsField[p] as T;
            index = i;
            break;
        }
        else
            pos++;
    }
}
// Check if the position should be the last position
if(index == -1 && pos == p) 
    index = items1Field.Count;

[tonyqus]

LGTM