State management for form fields

[vvalentin-lucca]

We want to be able to browse the required fields without getting an error:

• we don't want errors when ng-invalid and ng-touched are enabled;
• we want errors when ng-invalid, ng-touched and ng-dirty are enabled.

[lucienbertin]

i'm really not sure it's a good idea

[jeremie-lucca]

Guidelines were provided. Still in discussion. I'm closing it for now.