Enhancement on TreeTable

Hello all,

As the TreeTable extends the Table, if we put a Container inside a treetable that is not Hierarchical, the TreeTable should behave as a regular Table. At this moment, by default the icons for expanding/collasing on each node are visible even when we have a BeanItemContainer inside a TreeTable.

For my project a I had to extend the regular Table in order to store some extra info on each table. I had to repeat all this extra code for the TreeTable as the same extra behaviour was needed for it.

If the behaviour I describe here was implemented I wouldnt have to repeat all this code as the TreeTable would get all the code and I would get a regular Table when I used a non-hierarchical container inside a TreeTable.

In the future you could have just a Table that if received a Hirarchical container would build a TreeTable (with this behaviour optional of course)