Add csvt files when csv files are used as algorithm output

[qgib]

Author Name: Håvard Tveite (@havatv)
Original Redmine Issue: 18387

Redmine category:processing/qgis

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Some algorithms output csv files, and these often contain numeric fields. The output (csv) files are added to the layers panel and made available to the user. However, if there is no csvt file associated with a csv file, QGIS (GDAL/OGR) will assume that all the fields of the csv file are strings. Having numeric fields handled as strings is inconvenient for users, as they will not be able to for instance sort numerically, create graduated maps or do mathematics.

"Statistics by categories" is an example of an algorithm that outputs csv.

If a csvt file could be created alongside the csv file, QGIS (GDAL/OGR) should be able get the correct data type of each field, and the user would be able to work on the output table immediately and without data type problems.

This is relevant for both QGIS 2 and QGIS 3.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• category_id was changed from Unknown to Processing/QGIS
• tracker_id was changed from 1 to 2