Fixed: PostMaster Filter // possibility to Set more Email Headers (bug#10320).
Squashed commit of the following:

commit ee4913ca90f0c721944ad78c1c1daa6f6aa31a41
Author: s7design <otrs@s7designcreative.com>
Date:   Tue Apr 1 10:49:21 2014 +0200

    changed and cleaned code

commit 8e5f5776bbac4633b4d41e7c531e8d783c4218fa
Author: s7design <otrs@s7designcreative.com>
Date:   Tue Apr 1 10:49:09 2014 +0200

    changed and cleaned code

commit 73e301b52ba284b7fb3d602d5cccb12e3875e191
Author: s7design <otrs@s7designcreative.com>
Date:   Thu Mar 27 16:44:34 2014 +0100

    [Bug 10320] PostMaster Filter // possibility to Set more Email Headers

    Changed logic, added config item NumberOfHederFields, cleaned code.

commit ff1ee37d205c849e94315a069beeddcb2e062165
Merge: aff6dbb a7a2d13
Author: root <root@ubuntu.(none)>
Date:   Thu Mar 27 16:32:26 2014 +0100

    Merge remote-tracking branch 'upstream/master'

commit aff6dbb28f9c815ced086fc2846c41c87b36992a
Author: s7design <otrs@s7designcreative.com>
Date:   Wed Mar 26 17:35:46 2014 +0100

    [Bug 10320] PostMaster Filter // possibility to Set more Email Headers
    Changed the logic in the .tt file to not duplicate the code for every
    field. Now, the fields are created in loop.