added Octree class and included it in main
changed drawable_objects into a set instead of vector

will interface more similarly with Octree
added isBoundInFrustum function to wrap SphereInFrustum() function

will make it easier to interface with Octree
made ModelManager::boxOnBox static
finished implementing Octree but havent integrated yet

time to integrate and debug
integrated Octree with main.

still could use some improvements but it works
Merge branch 'master' of https://github.com/Milez213/CityTrial
removed old functions
reordered GameObject initializer to remove warning
made draw() more polymorphic and less copy and pasted
added structure for level of detail models
merge
made merge compile
Merge branch 'master' of https://github.com/Milez213/CityTrial
readded ballAtlas.bmp