HostSetup: Allow keys to be regenerated even with a custom setup

lib/setup/screens.dart

@@ -180,6 +180,12 @@ class GitHostSetupScreenState extends State<GitHostSetupScreen> {
                 _startGitClone(context);
               });
             },
+            regenerateFunction: () {
+              setState(() {
+                publicKey = "";
+              });
+              _generateSshKey(context);
+            },
             publicKey: publicKey,
             copyKeyFunction: _copyKeyToClipboard,
           );

lib/setup/sshkey.dart

@@ -91,11 +91,13 @@ class GitHostSetupSshKeyKnownProvider extends StatelessWidget {
 
 class GitHostSetupSshKeyUnknownProvider extends StatelessWidget {
   final Func0<void> doneFunction;
+  final Func0<void> regenerateFunction;
   final Func1<BuildContext, void> copyKeyFunction;
   final String publicKey;
 
   GitHostSetupSshKeyUnknownProvider({
     @required this.doneFunction,
+    @required this.regenerateFunction,
     @required this.copyKeyFunction,
     @required this.publicKey,
   });
@@ -124,10 +126,15 @@ class GitHostSetupSshKeyUnknownProvider extends StatelessWidget {
         const SizedBox(height: 8.0),
         PublicKeyWidget(publicKey),
         const SizedBox(height: 8.0),
+
         GitHostSetupButton(
           text: "Copy Key",
           onPressed: () => copyKeyFunction(context),
         ),
+        GitHostSetupButton(
+          text: "Regenerate Key",
+          onPressed: regenerateFunction,
+        ),
         const SizedBox(height: 16.0),
 
         // Step 2