Allow to change the submission date of a liaison

`owner:esanchez@yaco.es` `resolution_fixed` `type_enhancement`   |    by esanchez@yaco.es

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The submission date must be an editable field of the form to send (and to edit) a liaison.

Add a warning if the user enters a date that is seriously different than now.

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_Issue migrated from trac:653 at 2022-03-04 01:49:03 +0000_