Update checkpoints.cpp

Add checkpoint to 1st block in "good" chain.
Merge pull request #11 from Rav3nPL/patch-1

Update checkpoints.cpp
extra ckeckpoint info added.
fix: removed weird difficulty halving code (after block 175000).
removed non-validated checkpoint

 - block data not available on seednodes ; could also be malicious/wrong
 - exchanges are still relying on current chain......
 - commit d0088be15b removes the weird difficulty halving, at block
   175000+
diff halving removal: also use ema for >20mins blocks.
Merge remote-tracking branch 'terracoin/master' into terracoin-importaddress