[Poshuku CW] Fix rare segfault.

Sometimes frame could be destroyed before handleFrameLayout()
is called.
[Core] Handle toolbuttons and menus in ChildActionEventFilter.
[Util] Set icons in the main thread.
[Monocle] Smooth transform for PageGraphicsItem.
[Monocle] Support rotations in layout manager.
[Monocle] Exposed 90 degrees rotations in UI.
[Monocle] Added ArbitraryRotationWidget.
[Monocle] Rotation notification signal/slot in layout mgr.
[Monocle] Arbitrary rotation handling.
[Monocle] Removed unused variable.
[Monocle] Clear rotation on new doc.
[Monocle] Revert rotation button.