Added implementation of Asset Registry for Test Token (available inside docs/wallet-integration-guide/examples/scripts/15-multi-sync/_registry folder). The registry is started and stopped inside 15-multi-sync example script.
The following APIs are implemented:

1. Metadata API - endpoints '/registry/metadata/v1/info', 'registry/metadata/v1/instruments' and '/registry/metadata/v1/instruments/:instrumentId' (based on token-metadata-v1.yaml)
2. Transfer Instruction API - endpoints '/registry/transfer-instruction/v1/transfer-factory', '/registry/transfer-instruction/v1/:transferInstructionId/choice-contexts/accept', '/registry/transfer-instruction/v1/:transferInstructionId/choice-contexts/reject' and '/registry/transfer-instruction/v1/:transferInstructionId/choice-contexts/withdraw' (based on transfer-instruction-v1.yaml)
3. Allocation Instruction API - endpoint '/registry/allocation-instruction/v1/allocation-factory' (based on allocation-instruction-v1.yaml)
4. Allocation API - endpoints '/registry/allocations/v1/:allocationId/choice-contexts/execute-transfer', /registry/allocations/v1/:allocationId/choice-contexts/withdraw' and '/registry/allocations/v1/:allocationId/choice-contexts/cancel' (based on allocation-v1.yaml)
   The technical stack:
   NodeJS (built-in Wallet Gateway)
   Typescript (built-in Wallet Gateway)

HTTP API based on NodeJS is started inside example 15, the routes and REST API definitions are generated based on YAML files mentioned in points (1-4)

Example 15 uses newly created Test Toke registry for operations with TestToken asset