Implement new amendment majority semantics :

This implements the tracking of when an amendment achieved a majority
in the ledger, ensuring that there's always network-wide agreement
on which amendments have achieved a majority and how long they've
held it.

* New fields
* Change transactor changes
* AmendmentTable API and implementation changes
* Update amendment enabled status on validated ledgers
* Reinstate support for ledger sequence in fee transactions

src/ripple/protocol/impl/SField.cpp

@@ -226,6 +226,7 @@ SField const sfSignerEntry         = make::one(&sfSignerEntry,         STI_OBJEC
 // inner object (uncommon)
 SField const sfSigningAccount      = make::one(&sfSigningAccount,      STI_OBJECT, 16, "SigningAccount");
 SField const sfSigningFor          = make::one(&sfSigningFor,          STI_OBJECT, 17, "SigningFor");
+SField const sfMajority            = make::one(&sfMajority,            STI_OBJECT, 18, "Majority");
 
 // array of objects
 // ARRAY/1 is reserved for end of array
@@ -238,6 +239,9 @@ SField const sfSufficient      = make::one(&sfSufficient,      STI_ARRAY, 7, "Su
 SField const sfAffectedNodes   = make::one(&sfAffectedNodes,   STI_ARRAY, 8, "AffectedNodes");
 SField const sfMemos           = make::one(&sfMemos,           STI_ARRAY, 9, "Memos");
 
+// array of objects (uncommon)
+SField const sfMajorities      = make::one(&sfMajorities,      STI_ARRAY, 16, "Majorities");
+
 SField::SField (SerializedTypeID tid, int fv, const char* fn,
                 int meta, IsSigning signing)
     : fieldCode (field_code (tid, fv))