QWAT misses constraints in forms

[haubourg]

Since 2.16 It is possible to add constraints to widgets so that user can't validate a form that will not be accepted in the database. This ticket will list every constraint found until qgs project is inlined with DB's constraints

[ponceta]

I suggest to close this until any real need is shown.

[haubourg]

IMO this is required, How do your digitizers behave when they get postgis error messages? The ones I know REALLY don't like this