Improved performance and code quality in ticket overviews.

Squashed commit of the following:

commit d1d464b84b95436b6b0d3a294ee99a462b5a31c1
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Mon May 5 10:19:41 2014 +0200

    Fixed multiple JSLint, HTMLCheck and TT issues.

commit 98eef9f25cad505255204db691f56fe89619dc70
Merge: 631f7fb aca98da
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Mon May 5 09:43:22 2014 +0200

    Merge branch 'master' into feature-ticketoverview-performance-mn-master

commit 631f7fbbc89e05cbf4cc286d65cef3fcab5f8e4c
Merge: 784489e 6c3c3ba
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Tue Apr 29 16:06:19 2014 +0200

    Merge branch 'master' into feature-ticketoverview-performance-mn-master

commit 784489e6f1c07634473f088894485c4aa81f05c3
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Tue Apr 29 16:05:50 2014 +0200

    Removed print calls from ticket overviews. They now always use Output().

commit c4680e85f3a18f63f4754bf0ed9fe9c056920bea
Merge: 963f32a 2dc6c54
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Tue Apr 29 09:36:15 2014 +0200

    Merge branch 'master' into feature-ticketoverview-performance-mn-master

commit 963f32a5b55ae6ca46e6181a51c63b0858a8b7b9
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Tue Apr 22 14:36:23 2014 +0200

    Also improved rendering of medium and large view.

commit 86409458218de4df3c6cdb6848bce917b0a62bb8
Author: Marc Nilius <marc.nilius@otrs.com>
Date:   Tue Apr 22 13:47:43 2014 +0200

    Reduced number of calls to Output method for ticket overview.
Merge remote-tracking branch 'upstream/master' into otrs-master