Move ExchangeToken into separate file

Trust/Exchange/Types/ExchangeToken.swift

@@ -0,0 +1,15 @@
+// Copyright SIX DAY LLC. All rights reserved.
+
+import Foundation
+
+struct ExchangeToken {
+    let name: String
+    let symbol: String
+    let balance: Double
+}
+
+extension ExchangeToken: Equatable {
+    static func == (lhs: ExchangeToken, rhs: ExchangeToken) -> Bool {
+        return lhs.symbol == rhs.symbol
+    }
+}