Make [TableMatrix] allow controlling the height of squared cells

[Tor Esa Vestergaard]

The RowHeight and SquareCells arguments currently conflict with and override each other, because SquareCells makes the cells square by changing the height based on the width.

Repro:

public class TileRule
{
    public enum RuleType
    {
        This,
        NotThis,
        Ignore
    }

    [TableMatrix(RowHeight = 20,SquareCells = true,DrawElementMethod = "DrawCell")]
    public RuleType[,] tilingRules = new RuleType[3,3];

    private static RuleType DrawCell(Rect rect, RuleType value)
    {
        if (Event.current.type == EventType.MouseDown &&
            rect.Contains(Event.current.mousePosition))
        {
            value = value == RuleType.Ignore ? RuleType.This : value+1;
            GUI.changed = true;
            Event.current.Use();
        }

        if(value == RuleType.This) EditorGUI.DrawRect(rect.Padding(1),new Color(0.6f,1f,0.3f));
        if(value == RuleType.NotThis) EditorGUI.DrawRect(rect.Padding(1),new Color(1f,0f,0.3f));
        if(value == RuleType.Ignore) EditorGUI.DrawRect(rect.Padding(1),new Color(0.6f,0.6f,0.6f));

        return value;
    }
}

‌