Client : change name of variable overlap

Signed-off-by: Jean-François Erdelyi <jean-francois.erdelyi@etu.iut-tlse3.fr>
Client : Replace the grid by QuadTree

Signed-off-by: Jean-François Erdelyi <jean-francois.erdelyi@etu.iut-tlse3.fr>
Merge remote-tracking branch 'jf/master'

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>

Conflicts:
	client/index/QuadTree.js
	client/tests/test_quadtree.js