Added clearAllCentroidDataItems to CentroidHolder

This method was re-implemented in several places. Now it is in one
place.
Removed local distance measure from assignDataPatternsToParticle.

Most algorithms based on SinglePopulationDataClusteringIt... would
want to use the same distance measure throughout the algorithm.
StandardDataClusteringIterationStrategy now uses assignDataPatternsToParticle.

The pattern assignment code is exactly the same as the code in the
parrent class.
Moved assignment of pattern to centroid the quantisation error problem.

By moving pattern assignment to QuantisationErrorMinimisationProblem,
a lot of duplicate code is removed.

Moved SlidingWindow to QuantisationErrorMinimisationProblem to reduce
specialised/duplicate code.

Fixed bug in StandardDataClusteringIterationStrategy with regards to
the order of particle operations. Fitness should be calculated after
movement and pbest updates after that.