[what to contribute] design of virtual cluster?

[xwzheng]

admin

1. using vcmod to manage configuration（related issues: #906 ）
2. using vcuser to control accessiblity
3. using vcstat to show statitics of all vcs

general users

1. know which vc can be accessed
2. know the capacity and load of the vc

[Ziming Miao]

You could refer to api doc on this branch, notice it is still in updating. Now it support full vcmod and part vcstat
https://github.com/Microsoft/pai/blob/zimiao/queue_zookeeper/docs/rest-server/API.md

I will fork a new branch for whole vc updating feature later, we could keep this issue for tracking.

[Ziming Miao]

I folk a new branch, we could collabrate on it. You could refer its doc for your dev

[xwzheng]

I have push a design here. Need suggestions. thx.

[fan yang]

Code complete.
#1974
#1985
#1991
#2055