Added FromEmail field (makes it possible to pick from the list with official from email addresses)

Functional: In Administer-> CiviMail -> From Email Addresses you can define a list of official sender addresses for CiviCRM. This field allows you to select one of these email addresses as sender address.

Technical: The from email address is are stored in the option group from_email. The email address and name are combined in the "Example Name" <name@example.com>. This field splits this into two fields so both can be used.