[FEATURE] Add contentObject functionality to form MailPostProcessor

and introduce replyToEmail

If the form configuration is defined by TypoScript the following
items for the MailPostProcessor in ext:form have now
contentObject functionality:

* subject
* senderEmail
* senderName
* recipientEmail
* ccEmail
* replyToEmail (newly introduced, replyToEmailField as fallback)
* priority
* organization

This is disabled in the form wizard for security concerns.

Resolves: #68771
Releases: master
Change-Id: I13913b806b86bcfbe35d760b50e193a066cbcc4c
Reviewed-on: http://review.typo3.org/42290


Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>