Canceling clustering broken

[Christopher Keil]

As a result of implementing the single progressbar using the proper way with SwingWorker's publish() and process() methods, canceling the clustering process is broken at the moment.

Adapting the canceling procedure to the new code is in the works.

[Christopher Keil]

A fix has been impleneted that cancels every SwingWorker related to the process of clustering. When canceled, these SwingWorkers return appropriate values that signify a canceled operation. This is handled in the individual methods such that the original parent method ultimately handles the cancellation.

[Anastasia Baryshnikova]

Tested on 14-11-06. Fixed.