Feature #3914 - Set taxonomies from user defaults

Migration for taxonomy foreign keys in User model

Default taxonomies relations in models

Non-admin users should be able to clear taxonomies

Users form to set default taxonomies

Set current taxonomies from user defaults on login

String extraction and main_app

Actually test default taxonomies are set on login

Taxonomies defaults are editable by current user

i18n labels

Merge error fix in User

Users API returns default taxonomies

Fix: Users can edit their own default taxonomies