Fix handling of disabled recipes

[DaleStan]

As discussed briefly in #122, always show empty boxes for both the ingredients and products of disabled recipes. That is, they'll always look like this:

I also discovered the code that cleans up old links removes links if the item/fluid does not appear in any enabled recipes. I wanted the links to stay put when disabling and enabling recipes, and I couldn't concentrate on #122 with that behavior, so I changed the code to consider all recipes. If that change (f28d35f) should be discussed more, I can remove it from this PR.

[Dorus]

I also discovered the code that cleans up old links removes links if the item/fluid does not appear in any enabled recipes.

How so? It's not doing that for me in the master branch.

[DaleStan]

@Dorus It's more of a special case than I realized, but load this file, and disable and enable the small parts recipe. The links for bolts, copper cable, and iron gear wheel will get deleted.
links.yafc.txt

[shpaass]

Will test it today after 11 hours.

[veger]

Code changes look good to me.

I tried running it and while there are not visible issues, I do not see any difference with master branch when disabling/enabling. I guess I do not fully understand what I should try... 😞 But having the item icons hidden and the building/fuel icons visible looks good to me good.