Cw 110 integrate simple swap exchange (#459)

* add support for SimpleSwap exchange

* fix edit receive amount field

* fixed merge conflicts

* Fix issues from code review

tool/utils/secret_key.dart

@@ -25,6 +25,7 @@ class SecretKey {
     SecretKey('moonPaySecretKey', () => ''),
     SecretKey('sideShiftAffiliateId', () => ''),
     SecretKey('sideShiftApiKey', () => ''),
+    SecretKey('simpleSwapApiKey', () => '')
   ];
 
   final String name;