VC resource quota proportional update

[Anbang-Hu]

It has been a pain for us to manually update the resourceQuota in vc table when there is quota shifting from a vc to another. This PR

1. exposes a rest api /ResourceQuota for admin to update resourceQuota in vc. Resources for GPU sku will be set proportionally to requested GPU quota, while resources for CPU sku wikk be set proportionally to requested CPU quota. The restful API server will invalidate the local cache afterwards, saving us the extra step to restart it. @Gerhut need your help to add a dashboard page for cluster admin to manage VC quota.
2. add a command in ctl.py to query/update resource quota for vc:

   
   $ ./ctl.py quota show  # brief view on GPU (and CPU)
   vc          Standard_ND24rs(P40)  |
   --------  ----------------------  ---
   platform                      12  |
   vc1                            0  |

$ ./ctl.py -x quota show # detail view (GPU, GPU memory, CPU, memory) gpu:

vc Standard_ND24rs

---

platform 12 vc1 0

gpu_memory (Gi):

vc Standard_ND24rs

---

platform 288 vc1 0

cpu:

vc Standard_ND24rs

---

platform 72 vc1 0

memory (Gi):

vc Standard_ND24rs

---

platform 1344 vc1 0

$ ./ctl.py quota update --vc_name platform --sku Standard_ND24s --quota 13

[coveralls]

Pull Request Test Coverage Report for Build 3571

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.525%

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Totals
Change from base Build 3570:	0.0%
Covered Lines:	827
Relevant Lines:	874

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💛 - Coveralls