- Get the scroller orientation from the xib.
- Fix the nonsensical calculation of _isVertical when given bounds.
- Since orientation comes from the xib, had to re-nib2cib everything to be safe.
- Attributes set in IB are now obeyed.
- Added accessor methods to programmatically style _CPTableColumnHeaderView.
Since we don't have an NSCell and _CPImageAndTextView is supposed to be private, it's better to have the styling methods in _CPTableColumnHeaderView.