Allow to test email settings with trytond-admin

Following https://discuss.tryton.org/t/mail-test-in-administration-tree/2165

assigned to @pokoli

added trytond type::feature + 1 deleted label

review274681002 updated at https://codereview.tryton.org/274681002/#ps276661002

review274681002 updated at https://codereview.tryton.org/274681002/#ps289221004

review274681002 updated at https://codereview.tryton.org/274681002/#ps286641002

review274681002 updated at https://codereview.tryton.org/274681002/#ps260941005

review274681002 updated at https://codereview.tryton.org/274681002/#ps286731002

review274681002 updated at https://codereview.tryton.org/274681002/#ps258821002

review274681002 updated at https://codereview.tryton.org/274681002/#ps295101020

New changeset cbdb59e92439 by Sergi Almacellas Abellana in branch 'default':
Add option to send test email with trytond-admin
https://hg.tryton.org/trytond/rev/cbdb59e92439

added 1 deleted label and removed 1 deleted label

closed

New changeset ce4a36fb18cb by Sergi Almacellas Abellana in branch 'default':
Add option to send test email with trytond-admin
https://hg.tryton.org/tryton-env/rev/ce4a36fb18cb