modify db schema, merge `donor` and `guest`

- add `user` table
- use it to `donor` and `guest`
add Mojo helper for `user`

- wizard step 을 두고 user 와 guest 를 추가중
use right method of HTTP to new-borrower wizard
remove `guests/:id/size` route
add auto_increment key to `donor` and `guest` tables
use correct dbic obj method to `/guests/:id` tpl
add unique constraints to `user_id` to `donor & guest` tables
separate `id` and `user_id` from `guest`
off warnings
Merge branch 'guest2user' into develop

closes #28