Add validate option to trytond-admin

Following https://discuss.tryton.org/t/check-validity-of-existing-records/3422 The idea is to add a tool to trytond-admin to check records validity especially when doing an upgrade.

assigned to @ced

added trytond type::feature + 1 deleted label

added 1 deleted label and removed 1 deleted label

review312751002 updated at https://codereview.tryton.org/312751002/#ps311011003

review312751002 updated at https://codereview.tryton.org/312751002/#ps300791002

review312751002 updated at https://codereview.tryton.org/312751002/#ps331421002

review312751002 updated at https://codereview.tryton.org/312751002/#ps330011002

New changeset d27b905106dd by Cédric Krier in branch 'default':
Add validate option to trytond-admin
https://hg.tryton.org/trytond/rev/d27b905106dd

added 1 deleted label and removed 1 deleted label

closed

New changeset 526dd9395e12 by Cédric Krier in branch 'default':
Add validate option to trytond-admin
https://hg.tryton.org/tryton-env/rev/526dd9395e12