Added option to set TextField length for showTextInput()

the character length default was 12, and unchangeable afaik, so I added an option to change the character length, as well as suggesting a new character length for save file's name.
(I actually have no idea if this PR can be delivered correctly, wish me luck.)

SaveDialog.java

@@ -0,0 +1,61 @@
+package io.anuke.mindustry.ui.dialogs;
+
+import io.anuke.arc.Core;
+import io.anuke.arc.scene.ui.TextButton;
+import io.anuke.arc.util.Time;
+import io.anuke.mindustry.core.GameState.State;
+import io.anuke.mindustry.game.Saves.SaveSlot;
+
+import static io.anuke.mindustry.Vars.*;
+
+public class SaveDialog extends LoadDialog{
+
+    public SaveDialog(){
+        super("$savegame");
+
+        update(() -> {
+            if(state.is(State.menu) && isShown()){
+                hide();
+            }
+        });
+    }
+
+    public void addSetup(){
+        slots.row();
+        slots.addImageTextButton("$save.new", "icon-add", 14 * 3, () ->
+        ui.showTextInput("$save", "$save.newslot", 30, "", text -> {
+            ui.loadAnd("$saving", () -> {
+                control.saves.addSave(text);
+                Core.app.post(() -> Core.app.post(this::setup));
+            });
+        })
+        ).fillX().margin(10f).minWidth(300f).height(70f).pad(4f).padRight(-4);
+    }
+
+    @Override
+    public void modifyButton(TextButton button, SaveSlot slot){
+        button.clicked(() -> {
+            if(button.childrenPressed()) return;
+
+            ui.showConfirm("$overwrite", "$save.overwrite", () -> save(slot));
+        });
+    }
+
+    void save(SaveSlot slot){
+
+        ui.loadfrag.show("$saveload");
+
+        Time.runTask(5f, () -> {
+            hide();
+            ui.loadfrag.hide();
+            try{
+                slot.save();
+            }catch(Throwable e){
+                e.printStackTrace();
+
+                ui.showError("[accent]" + Core.bundle.get("savefail"));
+            }
+        });
+    }
+
+}