Templated Point class of any dimension
Overall, this seems to be a small but useful template.  However, there are a few things that I think might be improved.

Sorting requires more than swap

While the provided swap function would assist in some kind of sorting, without a comparison operator, we still can't actually sort.  This may well be by design, in which case a comment in the code pointing this out would be helpful.

Consider default constructor

There is no simple way at the moment to create a generic templated origin point (all coordinates zero).  This makes it a bit more difficult to create something like a distance_from_origin function that is generic.

Consider projection operator

It's often useful to project, say, a 3D point onto a 2D canvas.  This could also likely be made generic.

Do a range check

The distance function that measures from an axis does no range checking on the axis number and there does not seem to be a good generic way to add one.  Consider providing a range checking version.