Feature: Add Button and Modal to import DataFile

[arnaudfnr]

As a user, I want to populate my map with new form data.

Objective

Allow a user to import new data into the map

Context

Button -> onClick -> show Modal
Modal form:
-> File to upload
-> Kind of resource (form data or external data)
-> Resource name in the datapackage (list from datapackage resource retrieved from the backend #108
If external data:
-> ForeignKey : Resource Field -> Reference (ResourceName, MappedField)

Checks to implement :
Check if the file is correct
Check is headers are present
Catch error from coordo -> If data already exists, ask to overwrite or to cancel the operation, then resend the request with overwrite option.

No type inference needed (done on coordo side)