[db] Migration

[at15]

• [x] survey finished in #7
• [x] design doc
• [x] interface for migration tasks 484c455f1e1ea8a9e8269d8c0ac910c5b16e232d
• [x] create migration table 7c39e8a1d88f358c4ff715c154d0a9ef93a7851a
• [ ] create database
• [ ] generator for generating base migration task file
  • [ ] register migration
• [ ] example
  • [ ] user table
  • [ ] user's org, project etc.
  • [ ] seed dummy data

[at15]

should reopen when we start working on db