UI issues with collapse/expand in the profiler

[rthouvenin]

In the profiler, in Spyder 3.0.0dev, when root nodes are collapsed, clicking on the button "Expand one level down" expands the nodes correctly, but clicking one more time does not do anything even they are still levels to expand. Moreover, clicking on "Collapse one level up" does not do anything either.

In Spyder 2.7, the behaviour is different, but also wrong (expands three level down and collapses two levels up).