LPS-34188 New design for export dialog

Hey Nate,

This commit is the first step to adapt the export dialog to the new design. Basically we've kept all the backend logic as it is, and we've just rearranged the form and added some new UI features. Once we have the new backend features (e.g. progress bar) we will modify the dialog to explode them.

@ipeychev has already reviewed this code. As we want to apply this pattern to other dialogs (import, staging...), it's very important for us to have it validated by you, too. Please comment any change you make so we can document it and learn for the new dialogs.

Thanks!!

@juliocamarero
@JorgeFerrer
@matethurzo
@KocsisDaniel
@LeventeHudak