Moves the ion law picklists to an external txt

Credits to volundr @ goonstation for the idea and for the implementation that I included in _string_lists.dm

_Why is this needed, you ask?_
Basically: byond used to use a 16-bit (65536 values) string table. All strings go there. Lummox increased the limit, but ended up letting us write to areas that were supposed to be reserved for byond's use. The result is a lot of weirdness and crashes. Goon broke the limit a lot earlier, and they suggested that we move stuff like picklists to an external file in order to reduce the size of said string table. Note that this bug has just been fixed in upstream, however, since nobody knows when the next update will happen, I'm PRing this anyway.