Use WithTopology() to create/delete/show topology in the Topology Manager

[guoshiuan]

This PR also adds the following features:

• Validate the topology protobuf in the request, e.g., whether router config path is valid.
• Revise the unit test for topo.go

[coveralls]

Pull Request Test Coverage Report for Build 1918183156

• 31 of 103 (30.1%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.7%) to 58.054%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
topo/topo.go	30	34	88.24%
controller/server/main.go	1	69	1.45%

Files with Coverage Reduction	New Missed Lines	%
controller/server/main.go	1	29.95%

Totals
Change from base Build 1894775456:	-0.7%
Covered Lines:	1820
Relevant Lines:	3135

---

💛 - Coveralls