Lints src/models (#1572)

* resolve src/models/methods

* PaymentTransaction => Payment, remove empty returns

* fix common, method signatures

* fix checkCash

* handle complexity complaints

* fix jsdocs

* handle magic numbers

* finish models/transactions

* fix models/utils

* fix models/ledger

* fix ts issues

* fix tests

* fix modifiedoffercreatetransaction

* remove comments, fix additional TODO

test/models/utils.ts

@@ -9,7 +9,7 @@ import { isFlagEnabled } from "../../src/models/utils";
  */
 describe("Models Utils", function () {
   describe("isFlagEnabled", function () {
-    let flags;
+    let flags: number;
     const flag1 = 0x00010000;
     const flag2 = 0x00020000;