Devised bbox checks for every options.relation.
Simplified query options initialization.
Prevented _list/bbox-filter to parse an "undefined" req.body.

Seriously, whoever decided on "undefined" instead of "null", "{}" or any useful
alternative is the worst person!!!
Fixed some wrong arguments and variable names.
This reverts f7524feaeba1 because no risk no fun!!!
Simplified utils/pointInPolygon().

These relations have been a vector product to check if points are arranged
clockwise. I missed eliminating the difference when I replaced the function
calls with their explicit terms.