REGISTRAR: Allow editing submitted form to users
Created by: zlamalp
- We want users to be able to edit submitted applications.
- Added new api callback for it.
- PerunForm can now have 3 states, PREFILLED (initial on submission), EDIT (editing submitted) and PREVIEW. Each form item respect these states individually. Some form items are not editable/updatable (eg. login, non-editable fields). Also form items data of deleted template form item are not editable.
- Reworked, how we construct form item data before submission.
- Do not display mail verification notice on applications not related to mail to be verified.