various cleanups

I removed dead code, drew the robot position larger and added rotation, .gitignored build products, and adjusted the attenuation strategy on the historical map.  I also changed the swarm parameters to better utilize my desktop CPU and allow tracking of faster motion.  With 2500 particles, one core of a Phenom II X4 965 can keep up with the sensor (100ms) and track my position and orientation as I leisurely walk around my room.  This includes the time it takes to upload the buffer to the graphics card, which I am currently doing for every new scan.  Obviously, we can skip this expensive operation on the robot.