[IMP] project: kanban customization

[IMP] project: kanban customization
- stage model (project.task.type): add fields holding the eventual specific
legends for kanban states and star (priority) management
- project: task now have labels; you may use project to hold trainings
instead of tasks.
- project form: use label field on tasks statinfo to use the label
- project.task form: use kanban state customization using states_legend option;
- project.task kanban: use kanban column and kanban state cuztomization
using group_by_tooltip and states_legend options
- project_issue: issues now have labels, like tasks.
- issue: same kanban custo as for tasks
- update data and demo data

[IMP] web: statinfo widget now take an optional label_field option allowing
to have strings coming from another field present in the form view