As well as selecting more join rules.

We explicitly set a parent. We can't assign to
ApplicationWindow.transientParent though, only to
Window.transientParent, so we just call setTransientParent in C++.

Also fix a lot of warnings.

The actual reuseItems is still blocked on a few upstream bugs.

fixes #291

fixes #463

fixes #507

This reverts commit 74e32dd9.