Update for hard-fork, other migration updates

- TESTNET FLAG SET TO TRUE
- updated code to hard fork at const-based block height, uses all old specs until such height
- updated the checkpoints to match those of the 0.6.4 client
error compiling: currently hitting a compile error:
Undefined symbols for architecture x86_64:
  "Checkpoints::GuessVerificationProgress(CBlockIndex*)", referenced from:
      SetBestChain(CValidationState&, CBlockIndex*) in main.o
ld: symbol(s) not found for architecture x86_64