Changes a lot of things to make everything cleaner. Closes #3

Drops the idea of using serializable
Adds a new controller object which takes care of profiles and saving
Moves profile independent settings to its own file
Makes saving and loading from file a lot cleaner
Fixes the bug preventing lastly used profile from loading
Makes the profile object only do profile things
Moves gui initialization to the controller object
Updates vanilla version from 1.16.1 to 1.16.2
Moves backup to common functions

src/main/java/net/knarcraft/minecraftserverlauncher/userinterface/GUI.java

@@ -1,5 +1,7 @@
 package net.knarcraft.minecraftserverlauncher.userinterface;
 
+import java.io.File;
+
 /**
  * Describes a generic GUI
  */
@@ -42,4 +44,12 @@ public interface GUI {
      */
     void showMessage(String message);
 
+    /**
+     * Asks the user for a directory as a file object
+     *
+     * @param prompt <p>The prompt to show the user</p>
+     * @return <p>The directory given by the user</p>
+     */
+    File askForDirectory(String prompt);
+
 }