Add AT_ROOT constant.
Make use of AT_ROOT in ./includes/TestCases.test
Add json schema validator services.
Merge pull request #7 from v3kwip/json-schema-service

Add json schema service
Merge branch '7.x-1.x' into routing

* 7.x-1.x:
  Add json schema validator services.
  Make use of AT_ROOT in ./includes/TestCases.test
  Add AT_ROOT constant.
Fix fatal error when create new HookMenu object.