Rtree_intf functor now accepts Rtree_params module. It makes possible to change the limit of node's children (`max_nodes` variable, previously).
move Rtree_intf.Make to Rtree.Make
oasis setup
wip numeric module for generic bounding_box
add Bounding_box functor
add Bounding_box and Rtree module functors

Now its possible to create R-Trees for any numeric type
by parametrizing Bounding_box module with type you need (int, float, double).
fix OASIS setup due appearance of Bounding_box_intf module