Implement enhanced Ticket support:

Tickets are a mechanism to allow for the "out-of-order" execution of
transactions on the XRP Ledger.

This commit, if merged, reworks the existing support for tickets and
introduces support for 'ticket batching', completing the feature set
needed for tickets.

The code is gated under the newly-introduced `TicketBatch` amendment
and the `Tickets` amendment, which is not presently active on the
network, is being removed.

The specification for this change can be found at:
https://github.com/xrp-community/standards-drafts/issues/16

src/ripple/protocol/TER.h

@@ -60,7 +60,7 @@ enum TELcodes : TERUnderlyingType {
     telCAN_NOT_QUEUE_BLOCKS,
     telCAN_NOT_QUEUE_BLOCKED,
     telCAN_NOT_QUEUE_FEE,
-    telCAN_NOT_QUEUE_FULL
+    telCAN_NOT_QUEUE_FULL,
 };
 
 //------------------------------------------------------------------------------
@@ -113,10 +113,11 @@ enum TEMcodes : TERUnderlyingType {
     temBAD_TICK_SIZE,
     temINVALID_ACCOUNT_ID,
     temCANNOT_PREAUTH_SELF,
+    temINVALID_COUNT,
 
     // An intermediate result used internally, should never be returned.
     temUNCERTAIN,
-    temUNKNOWN
+    temUNKNOWN,
 };
 
 //------------------------------------------------------------------------------
@@ -158,6 +159,7 @@ enum TEFcodes : TERUnderlyingType {
     tefBAD_AUTH_MASTER,
     tefINVARIANT_FAILED,
     tefTOO_BIG,
+    tefNO_TICKET,
 };
 
 //------------------------------------------------------------------------------
@@ -195,7 +197,8 @@ enum TERcodes : TERUnderlyingType {
                      // burden network.
     terLAST,         // DEPRECATED.
     terNO_RIPPLE,    // Rippling not allowed
-    terQUEUED        // Transaction is being held in TxQ until fee drops
+    terQUEUED,       // Transaction is being held in TxQ until fee drops
+    terPRE_TICKET,   // Ticket is not yet in ledger but might be on its way
 };
 
 //------------------------------------------------------------------------------