Moved the implementation of updateVelocity/Position to the algorithms.

updateVelocity and updatePostion now simply updates those properties
with given arguments. It's now up to the algorithms to calculate the
new positions/velocities and send this information to the particles.
updatePosition still automatically updates the previous solution.

In most cases, this means the iteration strategies have to directly
access the velocity/position providers. In the case of the clustering
algorithms, the change is a bit more drastic.

Two ClusterParticle unit tests have become obsolete. A minor
adaptation to one of the unit tests in StandardDataClusteringIteration
StrategyTest should cover for the loss of the two unit tests.