nestboxes should be more flexible

[ab9rf]

The nestboxes plugin automatically protects all fertile eggs from harvesting; it would make more sense to give the player more control over this, both allowing for differential treatment by species (it makes little sense, for example, to farm ducks for meat, since they never yield any) and to be sensitive to the current population of the species in question.

[ab9rf]

this might be a good issue for someone to pick up. there's also no reason why nestboxes cannot be reimplemented as a lua script

[Birkow]

I have started working on script that would match this issue. For now I have some prototype prepared DFHack/scripts#1296
I'm open to any comments and feedback. It's my first script in lua and first mod to DF other than simple edits in raws so mistakes and questionable choices in there are likely.