Review vocabularies import popup

This popup is not clear enough currently.

Suggested improvements :

• in the main screen, one should be able to choose easily between [filling in the vocabulary / importing it] or referencing it. Similarly to the content views where we can reference a table layout.
• Automatically save once the csv file is selected.
• Present the sample file in a clearer way, currently the sample file is not visible enough.
• Provide immediate explanations about importing vs referencing, for instance in the popup title (<100 entries - import / 100+ entries - reference)