Add line controller tests. Fixed an issue when the number of data points changes...

Add line controller tests. Fixed an issue when the number of data points changes. When adding the tension to a point, get the same tension as the line if it has been overridden at the dataset level. When setting the hover style of a point, allow setting the radius independently of the regular radius. Use the hoverRadius property in point.custom or the dataset.pointHoverRadius. Allow setting the border width independently at the dataset level. Use dataset.pointHoverBorderWidth. This can be an array or a number.