rewrite of ThresholdTwoLevels (squashed)

I squashed the bugfixes.

commit e93dff0bb3fac67e9ff2d847f3eab8a18734a9de
Author: Markus Döring <webmaster@burgerdev.de>
Date:   Thu Feb 20 15:20:23 2014 +0100

    OpFilterLabels5d.propagateDirty now handles input slots correctly

commit 2e5e9a7489329b6f3e5a39fc38f45b62968262a7
Author: Markus Döring <webmaster@burgerdev.de>
Date:   Wed Feb 19 17:07:33 2014 +0100

    fixed endless loop bug

commit 1afbca5225d1b4f306b0891665421c0da2947787
Author: Markus Döring <webmaster@burgerdev.de>
Date:   Tue Feb 18 16:55:06 2014 +0100

    rewrite of ThresholdTwoLevels for 'large-t' data