let commands split by category

There are at least 2 groups of requirement currently. One is for cocos game project, such as `new`, `compile`, `run`, another is for updating cocos framework, such as `version`, `install`, `update`.

- project
	- new
	- run
	- compile
	- list  // open recent projects
	- deploy
	- clean
	- device
- engine
	- version
	- udpate
- help
- assets converter // convert the textures, audios into best file format for target platform. We need a resource manager in framework to do this.

So, if developers want to create new project , they should do:
`cocos project new` now.