[Imports] Virginia interstate exits

[Josh Doe]

I've asked for a list of interstate exits in Virginia from VDOT, which
they've provided me, and which I've summarized on this page:
http://wiki.openstreetmap.org/wiki/Virginia/Interstate_exits

They haven't yet formulated a suitable license agreement (though plan
to do so), so I can't actually use this data yet, but I wanted to
inform the list of my intentions once an agreement is in place. I
wouldn't quite call this an import, rather I prefer the term merge.

This data is quite basic, but important. Please let me know on the
talk page or here of your opinions.

-Josh