Added API for Long-Lived Transactions.
LongTx

  * Also added a better 'toString' to the VBox class
The transaction backing a Long Lived Transaction must allow writes.

  * Also, added support for Read-Only steps of Long Lived Transactions
Cannot use BPlusTrees in LogEntries
[jvstm-common] LongLivedTransaction now processes the write-set to create LogEntries
[jvstm-common] Added CodeGeneration support for VBox externalization