This commit includes the ability to search for k nearest neighbors using
a NEARBY command. When the LIMIT keyword is included and the 'meters'
param is excluded, the knn algorithm will be used instead of the
standard overlap+haversine algorithm.
NEARBY fleet LIMIT 10 POINT 33.5 -115.8
This will find the 10 closest points to 33.5,-115.8.
closes#136, #130, and #138.
ping @tomquas, @joernroeder, and @m1ome
