Mod config bug fixes, electron upgrade.

If the instance mods directory does not exist when the 'Add Drop-In Mod' button is clicked, it will be created.
The update selected server code has been modified. Previously, the server would be updated before the mod config was saved. This has been fixed so that the mod config is saved before the server is switched.
Updated electron to v3.0.10.

app/assets/js/scripts/landing.js

@@ -136,17 +136,20 @@ function updateSelectedAccount(authUser){
 updateSelectedAccount(ConfigManager.getSelectedAccount())
 
 // Bind selected server
-function updateSelectedServer(serverName){
-    if(serverName == null){
-        serverName = 'No Server Selected'
+function updateSelectedServer(serv){
+    if(getCurrentView() === VIEWS.settings){
+        saveAllModConfigurations()
     }
-    server_selection_button.innerHTML = '\u2022 ' + serverName
+    ConfigManager.setSelectedServer(serv != null ? serv.getID() : null)
+    ConfigManager.save()
+    server_selection_button.innerHTML = '\u2022 ' + (serv != null ? serv.getName() : 'No Server Selected')
     if(getCurrentView() === VIEWS.settings){
         animateModsTabRefresh()
     }
+    setLaunchEnabled(serv != null)
 }
 // Real text is set in uibinder.js on distributionIndexDone.
-updateSelectedServer('Loading..')
+server_selection_button.innerHTML = '\u2022 Loading..'
 server_selection_button.onclick = (e) => {
     e.target.blur()
     toggleServerSelection(true)