Child window support

- Added child window support with test app
- Miscellaneous cleanup
- Reformatted switches
More work on child windows

- Popovers are implemented as child windows.
- Renamed _CPAttachedWindow/_CPAttachedWindowView to _CPPopoverWindow/_CPPopoverWindowView, since that is its only use.
- The default for CPView -acceptsFirstMouse is now NO, per Cocoa. Subclasses override this as necessary.
- _CPWindowView -hitTest returns self it the mouse is within a resize region, which may be outside the window's frame.
- Fixed an off by one bug in CPDomWindowLayer -insertWindow:atIndex:, where inserting a visible window behind a window it is already behind would cause it to move up one from its intended position.
- Updated the ChildWindows and CPPopover test apps.
Final fixes for popovers as child windows

- Fixed case where a dangling transition function was left when closing a popover.
- Fixed case where closing a popover, moving the target view, then reopening the same popover would not reposition the popover when resizing the target view's window.
- Optimized repositioning of popover on target view change.
- Implemented transitional popovers via trapped mouse down events.
- Implemented dequeue: argument of CPApplication -setTarget:selector:forNextEventMatchingMask:untilDate:inMode:dequeue: and -setCallback:forNextEventMatchingMask:untilDate:inMode:dequeue:.
- Fixed some child window behavior when ordering/closing.
- Eliminated no longer necessary window close notification in CPPopover.
- Fixed window title in theme so it doesn't dim when window is main but not key.
Child window/popover fixes

- Added CPWindow -_parentWindowDidOrderInChild to notify a window when it is directly ordered in by a parent.
- Fixed observing of target view frame changes to work in all possible cases.
- Fixed typo in code introduced in last commit in CPApplication -sendEvent.
Merge pull request #1727 from slevenbits/slevenbits-child-windows

Child window support + popover fixes