removed concurrent aggregation requests

src/main/java/fucoin/AbstractNode.java

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

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

...ava/fucoin/actions/aggregation/ActionAggregationInit.java

...va/fucoin/actions/aggregation/ActionAggregationReply.java

.../fucoin/actions/aggregation/ActionAggregationRequest.java

...a/fucoin/actions/aggregation/ActionAggregationResult.java

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

...n/java/fucoin/configurations/MassWalletConfiguration.java

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

src/main/java/fucoin/wallet/AbstractWallet.java

src/main/java/fucoin/wallet/WalletImpl.java