Update Folder.java

- Folder no longer implements Serializable (this will break compatibility with older iterations of Folder). Epoch Launcher 1.2 will use Google GSON library for the serialization of classes.
- folderContents is no longer reinstated when using Folder(String newFolderName, ArrayList<AppInfo> newFolderContents). This pattern is recommended when dealing with an instance of Folder.
- Folder now overrides hashCode() and equals(Object obj) with it's own methods.