Support for retrieving clusters via CyRest

src/main/java/de/hhu/ba/yoshikoWrapper/CyActivator.java

...va/de/hhu/ba/yoshikoWrapper/graphModel/YoshikoResult.java

.../de/hhu/ba/yoshikoWrapper/graphModel/YoshikoSolution.java

...u/ba/yoshikoWrapper/taskFactories/CommandTaskFactory.java

...e/hhu/ba/yoshikoWrapper/taskFactories/YoshikoCommand.java

.../java/de/hhu/ba/yoshikoWrapper/tasks/GetClustersTask.java