prevent using same wallet name as existing (#391)

* Add wallet name validation

lib/core/validator.dart

@@ -40,8 +40,3 @@ class TextValidator extends Validator<String> {
 
   bool match(String value) => RegExp(pattern).hasMatch(value);
 }
-
-class WalletNameValidator extends TextValidator {
-  WalletNameValidator()
-      : super(minLength: 1, maxLength: 15, pattern: '^[a-zA-Z0-9_]\$');
-}

lib/core/wallet_name_validator.dart

@@ -0,0 +1,11 @@
+import 'package:cake_wallet/generated/i18n.dart';
+import 'package:cake_wallet/core/validator.dart';
+
+class WalletNameValidator extends TextValidator {
+  WalletNameValidator()
+      : super(
+            errorMessage: S.current.error_text_wallet_name,
+            pattern: '^[a-zA-Z0-9\-_ ]+\$',
+            minLength: 1,
+            maxLength: 33);
+}