This patch adds the `CPAppearance` class and uses it where needed.
There is nearly no impact, but in `_CPPopoverWindowView` where the
`CPPopoverAppearance` needs to be converted to a `CPAppearance` object
nib2cib support has also been added.
*This patch brings no new functionality.*
Previously, when making objj2objcskeleton on a category of a cappuccino class, the cocoa category was not a cocoa class but still a cappuccino class. For instance, a CPView category was still a CPView category instead of being a NSView category.
Fixed#2344