DolphinView: set the parent of layout in the ctor

DolphinView: set the parent of layout in the ctor

This silences a runtime warning:
QLayout: Attempting to add QLayout "" to DolphinView "", which already
has a layout

Remove redudant setLayout() calls, passing a parent widget to the
Q*BoxLayout ctor sets that layout as the top-level layout for that widget.