Reimplement focus mechanism.

The former implementation rely on changing of scene root nodes. This have
two problems: ancestor transforms are not taken into consideration when
calculating the viewpoint position, scene visibility limit is much smaller
for single node than for entire scene.

Reimplemented the functionality by defining bounding sphere to be set as
focus sphere, considering it during regular viewpoint calculation.
Switch to Qt debug dlls.

Needed for better tracing from Qt.
Fix item selection in scene tree.

There were a couple of regressions caused by migration from earlier
versions of Qt.
Removed Property and Modified columns from schene tree.
Fix boxfish rc file to actually show detail strings on Win7
Move dgd::controller instantiation into a separate dll.
Small cleanup and todo update.