Added possibility to negate postmaster filter settings, thanks to Renée Bäcker!

Squashed commit of the following:

commit e74dfe0fb9a53c749cec9e90a4716459bd355f92
Author: Martin Gruner <martin.gruner@otrs.com>
Date:   Thu Aug 15 14:30:39 2013 +0200

    Small fixes, added changes entry.

commit 697503daa8e22e0d5693d7eaeec812332c6f5519
Merge: b3ebf62 1c3a965
Author: Martin Gruner <martin.gruner@otrs.com>
Date:   Thu Aug 15 14:08:44 2013 +0200

    Merge branch 'reneeb_postmaster_not' of https://github.com/reneeb/otrs into postnegate

commit 1c3a9651738da773a5de2820ce277e09d9cb711c
Author: reneeb <github@renee-baecker.de>
Date:   Thu Aug 15 12:18:29 2013 +0200

    add column f_not to select statement

commit 3487d5d8f79540a8f8b4f062d1d65545da481377
Merge: 8fc2066 6f4b2d6
Author: reneeb <github@renee-baecker.de>
Date:   Thu Jul 25 01:09:57 2013 +0200

    resolve conflicts

commit 8fc20665ea1cce6d61096562708b3cde32592221
Author: reneeb <github@renee-baecker.de>
Date:   Thu Jul 25 01:04:32 2013 +0200

    add db changes to upgrade scripts

commit 90a321198e015761d2db3cc0baf0c83553b8d852
Author: reneeb <github@renee-baecker.de>
Date:   Thu Jul 25 00:42:27 2013 +0200

    add test mails

commit 4c866a53129c3605808a6720bb40ca08d403bb42
Author: reneeb <github@renee-baecker.de>
Date:   Mon May 20 06:19:53 2013 +0200

    add feature: negated regexes for postmaster filter

commit 6f4b2d6266ddd3ccdc41cd01d857f0b3bdc4a3b2
Author: reneeb <github@renee-baecker.de>
Date:   Mon May 20 06:19:53 2013 +0200

    add feature: negated regexes for postmaster filter