【MenuItem属性】
The MenuItem attribute allows you to add menu items to the main menu. The MenuItem attribute turns any static function into a menu command. Only static functions can use the MenuItem attribute.
To create a hotkey you can use the following special characters: % (ctrl on Windows, cmd on OS X), # (shift),& (alt), <b>_</b> (no key modifiers). For example to create a menu with hotkey shift-alt-g use "MyMenu/Do Something #&g". To create a menu with hotkey g and no key modifiers pressed use "MyMenu/Do Something _g".
Some special keyboard keys are supported as hotkeys, for example "#LEFT" would map to shift-left. The keys supported like this are: LEFT, RIGHT, UP, DOWN, F1 .. F12, HOME, END, PGUP, PGDN.
通过Selection类，可以获取当前编辑器选中对象的一些信息：
EditorApplication.ExecuteMenuItem，提供执行编辑器的菜单的能力。
EditorApplication类用于获取编辑器本身的信息，以及控制控制编辑器本身的行为。
参考：
1、file://localhost/Applications/Unity/Unity.app/Contents/Documentation/Documentation/ScriptReference/MenuItem.html
2、file://localhost/Applications/Unity/Unity.app/Contents/Documentation/Documentation/ScriptReference/Selection.html