Bucket Redistribution/Node Transfer bug fixes

D2TreeCore.java

* Changed constant type from raw static integers to a more organized enum "Key".
* Added proper names to modes ( enum Mode(String) ).
* Moved all bucket size info calls from redistData to storedMsgData.
* Fixed some bugs in forwardRedistributionRequest(Message).
* Fixed some bugs in forwardRedistributionResponse(Message).
* Added further debug messages.
* Now exceptions are printed in files.
Bug fixes in redistribution/transfer/extension.

D2TreeCore.java
* New nodes are now added randomly into buckets.
* Various bug fixes in forwardRedistributionRequest().
* Various bug fixes in forwardTransferRequest().
* Various bug fixes in forwardExtendContractRequest().
* Various bug fixes in forwardExtendRequest().
* Balance checks are halted if a redistribution is in process.
* Various bug fixes in forwardCheckBalanceRequest().

RoutingTable.java
* Changed formatting in method print(PrintWriter).

TransferRequest.java
* Fixed a bug in the constructor (the id of the pivot bucket wasn't stored).

ExtendContractRequest.java
* Now stores the total number of bucket nodes as a variable.