Investigate improving GridBox sizing

[jminer]

The size behavior of GridBox in IUP leaves something to be desired. You have to pick one line and one column that it will use to calculate the width and height respectively of the GridBox. To leave enough room for controls, you need to pick the widest line and tallest column. However, this is impossible in the face of translations. Column 1 could be a longer in English, but column 0 longer in German. I think using FITTOCHILDREN with every line and column is a work around, but I probably should test it more to see if there are disadvantages besides speed and consider doing it automatically.