Dynamize trusted validator list and quorum (RIPD-1220):

Instead of specifying a static list of trusted validators in the config
or validators file, the configuration can now include trusted validator
list publisher keys.

The trusted validator list and quorum are now reset each consensus
round using the latest validator lists and the list of recent
validations seen. The minimum validation quorum is now only
configurable via the command line.

src/ripple/core/Config.h

@@ -138,8 +138,6 @@ public:
 
     // Note: The following parameters do not relate to the UNL or trust at all
     std::size_t                 NETWORK_QUORUM = 0;         // Minimum number of nodes to consider the network present
-    int                         VALIDATION_QUORUM = 1;      // Minimum validations to consider ledger authoritative
-    bool                        LOCK_QUORUM = false;        // Do not raise the quorum
 
     // Peer networking parameters
     bool                        PEER_PRIVATE = false;           // True to ask peers not to relay current IP.
@@ -156,6 +154,7 @@ public:
     // Validation
     PublicKey                   VALIDATION_PUB;
     SecretKey                   VALIDATION_PRIV;
+    boost::optional<std::size_t> VALIDATION_QUORUM;     // Minimum validations to consider ledger authoritative
 
     // Node Identity
     std::string                 NODE_SEED;