Implement PolarVector class

PolarVector class represents a basic polar vector. It is needed for
various things with circles/sin/cos and in particular for
HeadBumpParticle to make randomly movind by circle particles.
Add DEPS to makefile (file dependencies)
Draw a second particle in HeadBumpParticle

To move a particle around a circle we add an operator+ to Vector class
which sum up a two Vectors.