Hydroponics refactor, part 1: Files.

No code actually modified, just moved from all over the place to a module folder.

defines/obj/hydro.dm split:
-Seeds into seeds.dm
-Tools like the analyzer, pest and weedkillers into hydro_tools.dm. Hatches and scythe from defines/obj/weapon.dm moved there too.
-Non-edible plants like nettles into grown_inedible.dm. Special procs in items/weapons/hydroponics.dm moved there.
-Biogenerator and hydroponics tray files moved.
Merge branch 'dev' of https://github.com/Baystation12/Baystation12 into hydro_refactor
Merge pull request #5212 from faerindel/hydro_refactor

Hydroponics refactor, part 1: Files.