Fix workbook and workflow models

 * There maybe multiple workbooks and workflows
   with the same names, but they must be in different projects
 * Workbooks and Workflows uniqueness across 2 columns now -
   'name' and 'project_id'

Fixes-bug: #1373320
Partially implements blueprint mistral-multitenancy

Change-Id: I3e8adb964217e2fdc25f332bfa1b4fca5f401a7e