Upload multiple projects in one go

[laurentS]

@SColchester suggested we might find a way to create multiple projects in one go if they're part of a same series.

A quick fix for this could be:

• keep the current form, but allow multiple AOI files to be selected at once
• if more than one file is loaded when "submit" is hit, then create a project for each using the same data for all, except the project number which could start from the value in the form, and then increase by one for each file. Files can be sorted alphabetically by filename to let the user have control of the order of the projects created.