collapsor jQuery plugin

[+] Menu 1
- Menu 1-1
- [+] Menu 1-2
  - Menu 1-2-1
  - Menu 1-2-2
[+] Menu 2
- Menu 2-1
- [+] Menu 2-2
  - Menu 2-2-1
  - Menu 2-2-2
Menu 3

Menu 1
- Menu 1-1
- Menu 1-2
  - Menu 1-2-1
  - Menu 1-2-2
Menu 2
Menu 3