cmd/geth, cmd/utils, core, rpc: renamed to blockchain

* Renamed ChainManager to BlockChain
* Checkpointing is no longer required and never really properly worked
when the state was corrupted.

eth/protocol_test.go

@@ -45,7 +45,7 @@ func TestStatusMsgErrors64(t *testing.T) { testStatusMsgErrors(t, 64) }
 
 func testStatusMsgErrors(t *testing.T, protocol int) {
 	pm := newTestProtocolManager(0, nil, nil)
-	td, currentBlock, genesis := pm.chainman.Status()
+	td, currentBlock, genesis := pm.blockchain.Status()
 	defer pm.Stop()
 
 	tests := []struct {