Bindings models wrapper

• Add Identity model.
• Add MessageSendReport model.
• Add Fact model.
• Add Message model.
• Add RestlikeMessage model.
• Add tests for models decoding and encoding (use example JSONs from Bindings as expected JSON schemas).

Tests/ElixxirDAppsSDKTests/FactTests.swift

@@ -2,7 +2,7 @@ import CustomDump
 import XCTest
 @testable import ElixxirDAppsSDK
 
-final class ContactFactTests: XCTestCase {
+final class FactTests: XCTestCase {
   func testCoding() throws {
     let jsonString = """
     {