Launcher improvements

Launcher windows are more Starter-like now:
- The scenery picker, vehicle list and keymapper buttons are now tied to the top portion of the screen.
- The current window is spanning the entire rest of the screen.
- Scenarios are now grouped into categories in the exact same way as Starter does.
- Some drawbacks include:
  - Currently you cannot edit the current trainset, as the vehicle picker window overwrites the scenario list window.
  - The GUI doesn't update when the screen resolution is changed.

launcher/keymapper.h

@@ -10,12 +10,12 @@ class keymapper_panel : public ui_panel
   public:
 	keymapper_panel();
 
-	void render() override;
+	void render_contents() override;
 	bool key(int key);
 
 private:
 	driverkeyboard_input keyboard;
-
 	user_command bind_active = user_command::none;
+	const std::string panelname = (title.empty() ? m_name : title) + "###" + m_name;
 };
 } // namespace ui