find_opposing_forces now returns a combination of all forces, rather than a prediction in what's important.

There aren't any semantic changes since this function is barely
implemented, but the variable names are now plural for instance.
The VolumeSide is now a bitmask.
Volume.h now will house functions from collision_util. It's been renamed volume.h.

To start, allProtrudingSides has been renamed extending_sides and is now
in volume.h. It takes advantage of the new VolumeSides bitmask mechanism
with a cleaner implementation while documented more simply.
Changed the description of the pong::math namespace.
Removed completely the collision_util file pair!

The functions are now in src/common/volume.h and src/common/volume.cpp.
With the isIn function now reimplemented as is_in in the
src/common/vector.h file, though not contained in the math namespace.
Added constraints to the PhysicsOptions structure.
Commented out a bit of new code in LocalServer.cpp, to avoid errors, etc.
Added tests for every helper in volume.h and did some last minute bug fixes.

extending_sides has also been moved below the intersecting function.