Added mapAnchors consensus rules, finished zcrawpour/zcrawreceive.

Some specifics on consensus changes:
* Transactions must be anchored to a real anchor in the chain.
* Anchors are pushed and popped during ConnectBlock/DisconnectBlock as appropriate.
* DisconnectTip triggers evictions, under some circumstances, of transactions in the
  mempool which are anchored to roots that are no longer valid.
* Commitments append to the tree at the current best root during ConnectBlock.

src/rpcserver.cpp

@@ -378,6 +378,7 @@ static const CRPCCommand vRPCCommands[] =
     { "wallet",             "walletpassphrase",       &walletpassphrase,       true  },
     { "wallet",             "zcrawkeygen",            &zc_raw_keygen,          true  },
     { "wallet",             "zcrawpour",              &zc_raw_pour,            true  },
+    { "wallet",             "zcrawreceive",           &zc_raw_receive,         true  }
 #endif // ENABLE_WALLET
 };