Service events scheduling

[tzununbekov]

Changes:

• serverless.yaml manifest supports events schedule:

  functions:
  go-lambda:
  source: go-lambda/main.go
  runtime: https://raw.githubusercontent.com/triggermesh/knative-lambda-runtime/master/go-1.x/runtime.yaml
  environment:
    foo: bar
  schedule:
  - cron: "*/5 * * * *"
    jsondata: '{"name":"triggermesh"}'
  - cron: "0 0 * * 6"
    jsondata: '{"weeklyBackup":true}'
    description: "some scheduled action"

• as a part of required changes knative dependencies were update, eventing legacy client removed :sparkles:
• integration tests updates

closes triggermesh/tm#194