fix(pay-form): ensure payment form shows on top

This fixes an issue where the payment form - initiated from an external
request payment link - would display under the connect dialog if that was
already open. This change ensures that the payment form always displays
on the top most layer.

Fix #284

app/components/Form/Form.scss

@@ -3,7 +3,7 @@
 .container {
   position: absolute;
   top: 0;
-  z-index: 10;
+  z-index: 20;
   height: 100vh;
   width: 100%;
   background: $spaceblue;
@@ -26,4 +26,4 @@
   svg {
     color: $white;
   }
-}
+}

app/routes/app/components/App.js

@@ -85,7 +85,6 @@ class App extends Component {
 
         <ContactModal {...contactModalProps} />
 
-        <Form formType={form.formType} formProps={formProps} closeForm={closeForm} />
         <ChannelForm {...channelFormProps} />
 
         <ReceiveModal {...receiveModalProps} />
@@ -101,6 +100,8 @@ class App extends Component {
             :
             <Network {...networkTabProps} />
         }
+
+        <Form formType={form.formType} formProps={formProps} closeForm={closeForm} />
       </div>
     )
   }