Jean datagrid inline editing

Ugh, this diff has a lot of irrelevant stuff ... 

Mainly, I want to work toward:

- you have the fields rendered without values, in creation mode, that's for a new row.
- then you also need the fields rendered in edit mode for the values of each row.
- then you also need the fields rendered in read mode for the values of each row.

You can ask the server for all of these at once at the start, and then ask again for any row that changes (edit/read mode rendered). 

The goal is for fields associated with datagrid columns to work like Plomino fields anywhere, (regarding widget, template override, validation, default formula, i18n, ...).