Differentiate tenders from EU institutions

[georgiana-b]

Besides tenders from each country Digiwhist also gives us tenders created by EU institutions.
These tenders have as value for country the country where the institution is (mostly BE and LU) and they are the reason why we have more tenders for certain countries than the ones present in that country's file.
They are also heavily skewing the data for BE and LU thus making the networks for these countries confusing.

To avoid these issues we decided to set the country attribute of these tenders to EU.