Introduce NFT support (XLS020)

Builds/CMake/RippledCore.cmake

@@ -420,6 +420,11 @@ target_sources (rippled PRIVATE
   src/ripple/app/tx/impl/DepositPreauth.cpp
   src/ripple/app/tx/impl/Escrow.cpp
   src/ripple/app/tx/impl/InvariantCheck.cpp
+  src/ripple/app/tx/impl/NFTokenAcceptOffer.cpp
+  src/ripple/app/tx/impl/NFTokenBurn.cpp
+  src/ripple/app/tx/impl/NFTokenCancelOffer.cpp
+  src/ripple/app/tx/impl/NFTokenCreateOffer.cpp
+  src/ripple/app/tx/impl/NFTokenMint.cpp
   src/ripple/app/tx/impl/OfferStream.cpp
   src/ripple/app/tx/impl/PayChan.cpp
   src/ripple/app/tx/impl/Payment.cpp
@@ -432,6 +437,7 @@ target_sources (rippled PRIVATE
   src/ripple/app/tx/impl/Transactor.cpp
   src/ripple/app/tx/impl/apply.cpp
   src/ripple/app/tx/impl/applySteps.cpp
+  src/ripple/app/tx/impl/details/NFTokenUtils.cpp
   #[===============================[
      main sources:
        subdir: basics (partial)
@@ -593,6 +599,7 @@ target_sources (rippled PRIVATE
   src/ripple/rpc/handlers/LogLevel.cpp
   src/ripple/rpc/handlers/LogRotate.cpp
   src/ripple/rpc/handlers/Manifest.cpp
+  src/ripple/rpc/handlers/NFTOffers.cpp
   src/ripple/rpc/handlers/NodeToShard.cpp
   src/ripple/rpc/handlers/NoRippleCheck.cpp
   src/ripple/rpc/handlers/OwnerInfo.cpp
@@ -687,6 +694,9 @@ if (tests)
     src/test/app/LoadFeeTrack_test.cpp
     src/test/app/Manifest_test.cpp
     src/test/app/MultiSign_test.cpp
+    src/test/app/NFToken_test.cpp
+    src/test/app/NFTokenBurn_test.cpp
+    src/test/app/NFTokenDir_test.cpp
     src/test/app/OfferStream_test.cpp
     src/test/app/Offer_test.cpp
     src/test/app/OversizeMeta_test.cpp
@@ -836,6 +846,7 @@ if (tests)
     src/test/jtx/impl/sig.cpp
     src/test/jtx/impl/tag.cpp
     src/test/jtx/impl/ticket.cpp
+    src/test/jtx/impl/token.cpp
     src/test/jtx/impl/trust.cpp
     src/test/jtx/impl/txflags.cpp
     src/test/jtx/impl/utility.cpp