limit neighbors to given number

src/main/java/fucoin/AbstractNode.java

...in/java/fucoin/actions/aggregation/ActionAggregation.java

...a/fucoin/actions/aggregation/ActionAggregationCancel.java

...n/java/fucoin/actions/aggregation/AggregationContext.java

src/main/java/fucoin/gui/SuperVisorGuiControlImpl.java

src/main/java/fucoin/gui/SuperVisorThreadGUI.java

src/main/java/fucoin/supervisor/SuperVisorImpl.java