Big refactoring:

- fix #14: now accepting configuration (in YAML) from file
- jobs definition is now on file, *not* in the "storage"
  (which is now used only for builds state)
- fix #9: definition of call arguments is now done in the YAML configuration
- #7 is now possible in the new database model
- #6 still work in progress (progress disabled for the moment)
- #4 is not needed anymore (no more edit forms)
- what about #3? (we still have build run/delete forms to protect..)

Tests still need to be ported before we can think of merging this.