Add Test to against runtimes.json to determine structure changes

Like @mrutkows commented in a PR #983, we need a way to validate changes at the API level. Please add a test in `wskdeploy` to verify changes against runtimes.json.

Review the API-level validation discussion in PR #983 and inspect runtimes.json alongside the wskdeploy test area. Add a test that verifies the expected structure and detects incompatible changes to runtimes.json; done means the test clearly fails for a structure change and passes for the current file.

Written by the indexing model from the issue text.