update bullet so it actually works

Moved the addSourceDirectory for physics/Bullet into the Engine/Source/CMakeLists.txt file that way it can actually appear where we expect it to in the solution explorer.

Engine/lib/bullet/examples/pybullet/unittests/utils.py

@@ -0,0 +1,8 @@
+def dot(A, b):
+  """Dot product between a 2D matrix and a 1D vector"""
+  return [sum([aij * bj for aij, bj in zip(ai, b)]) for ai in A]
+
+
+def allclose(a, b, tol=1e-7):
+  """Are all elements of a vector close to one another"""
+  return all([abs(ai - bi) < tol for ai, bi in zip(a, b)])