CloakCoin 2.0 'PHOENIX'

* BugFix: Fix issue with old Enigma requests being repeatedly expired.
* NewFeature: Implement blockchain downloader.
* NewFeature: Add SendCloakedToAddress RPC command.
* Enhancement: Implement Enigma Message system.
* Enhancement: Add "Copy TX ID" option to transaction view in QT Wallet.
* Enhancement: Speed up block loading.
* Enhancement: Improve PoS block validation.
* Enhancement: New Feature: Implement automatic wallet backup system.
* Enhancement: Refactor CloakShield to decrease traffic and improve reliability.
* Enhancement: Refactor and improve Enigma input selection code.
* Enhancement: Switch blockchain database format to LevelDB.
* Enhancement: Remove 'NumSplits' from the Enigma process and increase min-cloakers by one.
* BugFix: Retain coin-lock once a Cloaker signs an Enigma transaction until new block is recieved.
* BugFix: Stop Cloakers supplying an extra blank output address causing the Enigma transaction to fail.
* Misc: Rename PoSA to Enigma.