added hashtable based PairManager, thanks Pierre Terdiman and Erin Catto
improved friction in 'cachefriendly' solver
moved 'refreshcontactpoints' into collision detection, instead of solver
avoid linear search for contact manifolds, by storing an index
ignore margin for sphere shape (its entire radius is already margin)
avoid alignment checks in BVH serialization, they don't compile on 64-bit architectures
made 'bomb' box more heavy
Same interface but less features (push_back, pop_back, clear, size, [] etc).
To prepare for SIMD/SSE code: Added #define ATTRIBUTE_ALIGNED16(a) __declspec(align(16)) a
