cubicweb #525245 devtools: have a default csv format compatible with import [deprecated]

We should have a clear text import/export format easily reusable.

For example in order to easily synchronize data between a demo instance and code repository.

See cubicweb/web/views/csvexport.py to match the requirement of the input format defined in cubicweb/devtools/dataimport.py.

Maybe a new csv input form view can be useful as well.

priorityminor
typeenhancement
done in<not specified>
load0.000
load left0.000
closed by<not specified>