Very major changes

Added templated Segment class
AABB::getXXCorner methods are now templated
Added templated AABB::getXXSegment methods
Removed useless Cell::getQuery
Name refactoring
Removed useless GridInfo::checkEdges
getSigned2DTriangleArea and isSegmentIntersecting are now templated and
use Segment class
Added World::clear
Added templated World::getResolver and World::getSpatial (they
statically cast resolver and spatial)