Export butcher factor to json.

Add BUTCHER qualities to all items with a valid butcher factor.
Uses the same value that would have been returned by the the calculation in item::butcher_factor.
Invert the meaning of the BUTCHER tool quality.

As KA101 pointed out, higher tool quality level is supposed to mean better tool.
The BUTCHER quality should be consistent with this.

This commit invert the butcher factor values in the json data, it also inverts the meaning in the code (chooses item with highest butcher factor, etc.).
This does not change the actual game mechanics.
Merge branch 'butcher-this' of https://github.com/BevapDin/Cataclysm-DDA into butcher