Convert payments row backbone view into JS

Per our definition newly introduced files should be JS instead of Coffeescript.

backend/app/assets/javascripts/spree/backend/views/payment/payment_row.js

@@ -0,0 +1,35 @@
+Spree.Views.Payment.PaymentRow = Backbone.View.extend({
+  events: {
+    "click .js-edit": "onEdit",
+    "click .js-save": "onSave",
+    "click .js-cancel": "onCancel"
+  },
+
+  onEdit: function(e) {
+    e.preventDefault();
+    this.$el.addClass("editing");
+  },
+
+  onCancel: function(e) {
+    e.preventDefault();
+    this.$el.removeClass("editing");
+  },
+
+  onSave: function(e) {
+    var view = this;
+    var amount = this.$(".js-edit-amount").val();
+    var options = {
+      success: function(model, response, options) {
+        view.$(".js-display-amount").text(model.attributes.display_amount);
+        view.$el.removeClass("editing");
+      },
+      error: function(model, response, options) {
+        show_flash('error', response.responseJSON.error);
+      }
+    };
+    e.preventDefault();
+    this.model.save({
+      amount: amount
+    }, options);
+  }
+});