Add select/prefetch related to exports

[gutard]

Add select/prefetch related to FormatList views (exports). For now I removed zoning from attributes as it triggers a request for each row. Maybe we could add an annotate to handle this.

[cypress[bot]]

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Test summary

18 • 0 • 0 • 0

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Run details

Project	Geotrek-admin
Status	Passed
Commit	77aab9ad07
Started	Mar 16, 2021 2:39 PM
Ended	Mar 16, 2021 2:42 PM
Duration	02:59 💡
OS	Linux Ubuntu Linux - 14.04
Browser	Electron 80

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[LePetitTim]

IMHO, it will not be possible to merge this PR with modifications on django-geojson + custom columns @submarcos @Chatewgne

[LePetitTim]

@gutard This will not be merged : Custom columns make it obsolete