Use QSharedPointer for cross-thread Link references

Also many LinkManager API changes to further isolate all link
management inside LinkManager.

src/ui/QGCToolBar.cc

@@ -676,10 +676,8 @@ void QGCToolBar::_connectButtonClicked(bool checked)
             // Get the configuration name
             QString confName = _linkCombo->currentText();
             // Create a link for it
-            LinkInterface* link = _linkMgr->createLink(confName);
+            LinkInterface* link = _linkMgr->createConnectedLink(confName);
             if(link) {
-                // Connect it
-                _linkMgr->connectLink(link);
                 // Save last used connection
                 MainWindow::instance()->saveLastUsedConnection(confName);
             }

src/ui/toolbar/MainToolBar.cc

@@ -163,10 +163,8 @@ void MainToolBar::onConnect(QString conf)
             // We don't want the combo box updating under our feet
             LinkManager::instance()->suspendConfigurationUpdates(true);
             // Create a link
-            LinkInterface* link = LinkManager::instance()->createLink(_currentConfig);
+            LinkInterface* link = LinkManager::instance()->createConnectedLink(_currentConfig);
             if(link) {
-                // Connect it
-                LinkManager::instance()->connectLink(link);
                 // Save last used connection
                 MainWindow::instance()->saveLastUsedConnection(_currentConfig);
             }

src/ui/uas/UASListWidget.cc

@@ -118,7 +118,7 @@ void UASListWidget::updateStatus()
         LinkInterface* link = i.key();
 
         // Paranoid sanity check
-        if (!LinkManager::instance()->getLinks().contains(link))
+        if (!LinkManager::instance()->containsLink(link))
             continue;
 
         if (!link)