Fixed: CPComboBox don't close when clicking on the scroll

Previously CPComboBox don't close when clicking on the scroll, now it does

Fixed #1991
Fixed: The delegate method shouldSelectItem doesn't work in CPOutlineView

Previously the delegate method shouldSelectItem didn't work in CPOutlineView.
It didn't work because the checking method _delegateRespondsToSelectionIndexesForProposedSelection and _delegateRespondsToShouldSelectRow didn't check if the real delegate of the outlineView implemented the methods
Changed comment
Merge pull request #2006 from Dogild/outlineView-selectItem

Fixed: The delegate method shouldSelectItem doesn't work in CPOutlineView
Merge pull request #2004 from Dogild/comboBox-trapMouse

Fixed: CPComboBox don't close when clicking on the scroll
Fixed: Return a Number from CPNumber>>numberWithBool:

The Cocoa signature for this method
	+ (NSNumber *)numberWithBool:(BOOL)value
implies that a number is being returned. In Cappuccino a Boolean is returned.

This leads to some problems e.g. in
addObserver:forKeyPath:options:context: with CPKeyValueObservingOptionPrior
and observeValueForKeyPath:ofObject:change:context: with CPKeyValueObservingOptionPrior.

Setting CPKeyValueObservingOptionPrior leads to CPKeyValueChangeNotificationIsPriorKey being set to 1 (which should be equal to [NSNumber numberWithBool:YES] as documented in https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Protocols/NSKeyValueObserving_Protocol/Reference/Reference.html. The actual value though is true as [CPNumber numberWithBool:YES] does not return a number but a boolean. This commit fixes this issue.
Merge pull request #2007 from krodelin/fix-CPNumber-numberWithBool

Fixed: Return a Number from CPNumber>>numberWithBool: