Bug 14969: Remove C4::Dates from serials/*.pl files

Bug 14969: Remove C4::Dates from serials/*.pl files

Warning: This area is a mess, especially with date management.

For the same reasons as other "Remove C4::Dates from*" patches, this one
will deal with the serials module.

Note that this patch add the datepicker on 3 input fields (on
serials/subscription-detail.tt and serials/subscription-renew.tt).
There was also weird behavior when the dates were invalid. Now default
to undefined. But with the datepicker it will reduce the number of
cases even if the user is still allowed to fill invalid dates.

Test plan:
1/ Create a subscription, fill the first issue pub date and the
subscription start date.
You can fill or not the end date.
Play with the numbering pattern and confirm that there are generated as
before this patch.
2/ On the check expiration page, confirm that the dates are correctly
displayed.
3/ Renew the subscription and confirm that the behavior is correct.
4/ Go on the subscription history page and confirm you have now the
datepicker plugin set on the 2 date fields.

QA notes: The startdate, histstartdate and enddate are not used in
the serials-collection template, this patch removes them from the pl
script.

Tested on top of 15166 15168 15171, full browser reload for date pickers.
Note for 4/: It is the link in tab planning on subscription
detail page, near "Manual history" (if manual history is enabled).
Works as advertised.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>