Clip angling and lake data before doing spatial join

[woodsp]

We want to analyse just those angling events that happen on a lake that intersects with the continental US. So future workflow in spatialjoin.r should be:

1. Clip custom NHD database to waterbodies that intersect with continental US. No AK, HI, Puerto Rico.
2. Clip angling events to the bbox of the custom NHD database.
3. Then do the angling x waterbody intersection.