A unique group is a radiobutton group unique among the whole page hierarchy,
while the {@link setGroupName GroupName} specifies a group that is unique
among the control's naming container only.
For example, each cell of a {@link TDataGrid} is a naming container.
If you specify {@link setGroupName GroupName} for a radiobutton in a cell,
it groups together radiobutton within a cell, but not the other, even though
they have the same {@link setGroupName GroupName}.
On the contratry, if {@link setUniqueGroupName UniqueGroupName} is used instead,
it will group all appropriate radio buttons on the whole page hierarchy.
Note, when both {@link setUniqueGroupName UniqueGroupName} and
{@link setGroupName GroupName}, the former takes precedence.
