cubicweb #1936782 refactor system/user preferences view to make it less monolithic [resolved]

so that one can easy override part of it

prioritynormal
typeenhancement
done in3.14.0
load0.300
load left0.000
closed by#58f696c0f5b3 [cwproperties] refactor properties form to make it partly overrideable easily (closes #1936782)