Event bbox does not handle crossing the anit-meridian

[pwoods25443]

When Min, Max and Avg are computed for lat/lon in events, we do not take into consideration events that span the antimeridian.

for example, an event containing the points:

lat	lon
0	-178
1	-179
1	179
0	178

will have

MIN(lon) = -179
MAX(lon) = 179
AVG(lon) = 0

when what we want is

MIN(lon) = -178
MAX(lon) = 178
AVG(lon) = 180 (or -180)