* Dock panels shouldn't have any frame border or anything like that.
* They should have an external margin of 3 pixels at their border,
but then no further margins on the layouts (like sub-controls for
the pipeline state views.
* Toolbars should be Raised & Panel frames. Later we'll replace them
with actual QToolBars to better customise the painting.
* This was only added because the default tree widget controls don't
render any grid lines. Now that we're custom drawing them, the row
colors are distracting and can be confusing on themes where the
selected row is very faint.
* QShortcut falls down on duplicates. It can have activatedAmbiguously
events, but these happen in arbitrary order and the shortcuts on
menu items just swallow the ambiguous activate so it's not useful.
* Instead we just let MainWindow pick up ShortcutOverride events and
consult a mapping of which shortcuts to use. We can use a smarter
selection method to choose the more 'local' shortcut if two shortcuts
that conflict exist.
* Annoyingly although Qt has an internal bool allowUserMoveOfSection0
which does exactly what we want allowing the tree column to be
movable, we can't enable it because it's private. So instead we have
to re-implement section moving ourselves.
* Minor tweak - also made RDTreeWidgets non-movable by default since
usually we don't want to allow it.
* Since we're promoting everything, we reset the behaviour of
RDTreeWidget so that it's not doing anything different by default.
* RDTreeWidget's interface is a bit different, exposing some useful
things like a single selected item and so on.
* We also can't set columns in the Qt Creator UI anymore, so we set them
from code.
* It seems due to deficiencies in Qt's design, there will be a
substantial need for these small custom subclasses just to add basic
functionality that should have been present in the original. So we'll
adopt a naming scheme of QFooBar -> RDFooBar for this 'almost the
same widget' type subclassing, compared to more custom/changed ones.
* GUIInvoke helper changed to use QMetaObject::invokeMethod which works
on threads better.
* LambdaThread helper class now has a thread member, it doesn't derive
from thread (this seems to be recommended practice).
baldurk