Abstract: Allow filter inserters to be configured to filter for negative signals (or any other condition than the default positive).

At the moment, when filter inserters are connected to the circuit network and set to "set filters" mode, they will grab any item for which they receive a positive ...

I would implement it as follows:
Screen Shot 2016-07-20 at 12.47.21 PM.png
The belt is set to read in "hold" mode. Both deciders have their condition set to (stone) < 1 and are connected by green wire to the belt. The top combinator outputs 1 on red if it's true, and the bottom combinator outputs ...

When using inserters to read their hand in "hold mode", I get that items are sometimes counted twice in my circuit network in situations when I do not expect them to be. In particular, consider the following setup:
Screen Shot 2016-07-20 at 9.33.14 AM.png
Were the inserter activated, I would ...