validate *.api when generating Node.js JavaScript interface

[ehennum]

Validate against the JSON schema when generating the Node.js JavaScript interface for a *.api file

Internal bug: 53357

[ehennum]

The code generation of the Data Service unit tests under test-basic-proxy/lib/generated uses the validation and
thus provides positive cases.

This unit test provides negative cases:

test-basic-proxy/lib/negative/badGenerationTest.js

I'm thinking that's sufficient confirmation that the JSON schema validation works -- see any need for additional coverage?

[georgeajit]

Unit tests run fine on Jenkins. NodeAPIUnitTests_develop-b10_0 job.